^,^#Aii^ 


Vl7  A  f  t  M  ,  S  V 


1  ■    \, 


m' 

*'  ■  ■ , 

B' 

]i.     \; 

^■. 

,'^?m 


'Yl  I  ■.    ■  .     1  ■-  1  '  * 


■  \  ■  \ 


. '■'     I  l" 


'\S 


V  >    i 


'       1     ■      '  V 


'.l!\'i 


5^;'?!V. 


'  ■  1     -.A 


^  ,•'  V  >  -  ■  ( 


m2  i.  M.  Bill  ^Xtbrarg 


Nortlr  (Eamltna  S^tnU  Hmnerfiilg 

Gift  From  The 
J.  M.  PicKELL  Family 

QH567 
M5 


N.C.  STATE  UNIVERSITY     D.H.  HILL   LIBR^R^ 


S00278621   Q 


THIS  BOOK  IS  DUE  ON  THE  DATE 
INDICATED  BELOW  AND  IS  SUB- 
JECT TO  AN  OVERDUE  FINE  AS 
POSTED  AT  THE  CIRCULATION 
DESK. 


NOV  -  4  1987 


N''>v  1  8  tya? 


FEB  2  4  1988 


^'UG-^  1993 


\  ?  1993 


MAY  2  9  1996 


100M/7-85 


EVOLUTION 


AND    ITS    RELATION   TO 


RELIGIOUS  THOUGHT 


BY 

JOSEPH   LE   COI^TE 

AUTHOR   OF    "religion    AND    SCIENCE,"    ETC. 

AND   PROFESSOR   OF    GEOLOGY    AND   NATURAL    HISTORY    IN   THK 

UNIVERSITY    OF    CALIFORNIA 


NEW   YORK 
D.   APPLETON  AND   COMPxYNY 

1888 


COPYEIGHT,   1888, 

By  D.   APPLETON  AND  COMPANY. 


PEEFACE. 


The  subject  of  the  following  work  may  be  expressed 
in  three  questions :  What  is  evolution  ?  Is  it  true  ? 
What  then  ?  Surely,  there  are  no  questions  of  the  day 
more  burning  than  these.  Much  has  been  written  on 
each  of  them,  addressed  to  different  classes  of  minds: 
some  to  the  scientific,  some  to  the  popular,  and  some  to 
the  religious  and  theological ;  but  nothing  has  yet  ap- 
peared which  covers  the  whole  ground  and  connects 
the  different  parts  together.  Much,  very  much  has  been 
written,  especially  on  the  nature  and  the  evidences,  of 
evolution,  but  the  literature  is  so  voluminous,  much  of 
it  so  fragmentary,  and  most  of  it  so  technical,  that  even 
very  intelligent  persons  have  still  very  vague  ideas  on 
the  subject.  I  have  attempted  to  give  (1)  a  very  con- 
cise account  of  w^hat  we  mean  by  evolution,  (2)  an  out- 
line of  the  evidences  of  its  truth  drawn  from  many  differ- 
ent sources,  and  (3)  its  relation  to  fundamental  rehgious 
beliefs.  I  have  determined,  above  all,  to  make  a  book 
so  small  that  it  may  be  read  through  without  much  ex- 
pense of  time  and  patience.  But  the  subject  is  so  large 
that  in  order  to  do  so  it  was  necessary  to  sacrifice  all 
but  what  was  most  essential,  and  to  forego  all  redun- 


iy  PREFACE. 

daDcy  (the  bane  of  so-called  popular  science)  even  at  the 
risk  of  baldness  and  obscurity.  Nevertheless,  I  hope 
that  the  first  and  second  parts  will  be  found  not  only 
interesting  to  the  intelligent  general  reader,  but  even 
profitable  to  the  special  biologist.  I  have  tried  to 
make  these  parts  as  untechnical  as  possible,  but  I 
hope  not  on  that  account  the  less  scientific.  For  I  am 
among  those  who  think  that  it  is  not  necessary  to  be 
superficial  in  order  to  be  popular — that  science  may  be 
adapted  to  the  intelligent  popular  mind  without  ceasing 
to  be  science. 

The  third  part  seems  to  me  still  more  important  just 
now.  There  is  a  deep  and  widespread  belief  in  the 
popular  mind,  and  even  to  some  extent  in  the  scientific 
mind,  that  there  is  something  exceptional  in  the  doc- 
trine of  evolution  as  regards  its  relation  to  religious 
thouo-ht  and  moral  conduct.  Other  scientific  theories 
have  required  only  some  modifications  of  religious  con- 
ceptions, but  this  utterly  destroys  the  possibility  of  all 
religious  belief  by  demonstrating  a  pui-e  materialism. 
'Now  this,  I  believe,  is  a  complete  misconception. 
Thinking  men  are  fast  coming  to  see  this ;  some,  in- 
deed, have  mistaken  tlie  change  for  a  reaction  against 
evolution.  It  is  a  reaction  not  against  evolution,  but 
only  against  its  materialistic  implication.  Evolution  is 
more  and  more  firmly  established  every  year.  The  tide 
of  conviction  is  one  which  knows  no  ebb.  Some  clear 
statement,  in  brief  space,  of  its  true  relation  to  religious 
thought  seems,  therefore,  very  important  at  this  time. 

Berkeley,  Cal.,  May,  1887. 


COISTTEI^TS. 


PAKT  I. 

WRAT  IS  F VOLUTION? 
CnAPTER  I. 

ITS    SCOPE   AND    DEFINITION. 

PAGE 

A  type  of  evolution — Development  of  an  egg     .....       3 

Universality  of  evolution — Pervades  all  nature  and  concerns  all  de- 
partments of  thought — One  half  of  all  science — Illustrated  (1) 
by  human  body,  (2)  by  solar  system,  (3)  by  society,  (4)  by  earth, 
(5)  by  organic  kingdom — The  term  evolution  usually,  but  not 
rightly,  confined  to  this  last       . 3 

Definition  of  evolution — /.  Progressive  change — Shown  in  the  animal 
body,  or  the  Ontogenic  series — In  the  animal  scale,  or  the  Taxo- 
nomic  series — In  the  geological,  or  Phylogenic  series — The  three 
series  similar,  though  not  identical 8 

//.   Change  according  to  certain  laivs — Three  laws  of  succession  of 

organic  forms .11 

(a)  Laio  of  differentiation — Early  forms  are  generalized ;  afterwards 
separated  into  specialized  forms — Illustrated  by  fishes,  by  birds 
— Whole  process  of  differentiation  illustrated  by  growth  and 
branching  of  a  tree  .         .         .         .         .         .         •         •         .11 

{b)  Laio  of  progress  of  the  w7<o^e— Mistake  of  confounding  evolution 
with  upward  progress — How  far  true,  and  how  far  false — Illus- 
trated by  branching  tree — Examples  of  this  mistake  in  the 
popular  mind — In  the  scientific  mind 13 

(c)  Laio  of  cyclical  movement— ^hoyvn  in  geological  history — Age  of 
raollusks^hes,  reptiles,  mammals,  man— Illustrated  again  by 


^i  CONTENTS. 

PAGE 

a  brancliing  tree — Increasing  complexity  as  well  as  beigbt — 
Illustrated  by  diagram 16 

The  above  three  laxos  are  laws  of  evohition — Differentiation — Shown 

in  the  developmeut  of  an  egg,  the  type  of  evolution  .         .         .19 

Progress  of  the  whole — Not  progress  of  all  parts — Shown  in  the  de- 
velopment of  an  egg  .         .         .         .         .         .         .         .22 

Cyclical  movement — Less  fundamental  than  other  two — Shown  in 
Ontogeny  of  body,  of  mind — Increasing  complexity — Necessity 
of  continued  advance — Otherwise  deterioration — All  these  laws 
shown  in  progress  of  society — Differentiation  shown — Progress 
of  the  whole  but  not  of  all  parts  shown — Cyclical  movement 
shown — In  social  evolution,  however,  there  is  another  element, 
viz.,  conscious  voluntary  progress — This  kind  of  evolution  con- 
trasted with  the  other        .         .         ,         .         .         .         .         .22 

///.  Change  by  mecms  of  resident  forces — This  is  the  point  of  dis- 
pute— Sense  in  which  we  use  term  resident  forces — Does  not 
touch  question  of  origin  of  natural  forces  .         .         .         .2*7 

The  two  vieiDs  of  the  origin  of  organic  forms  brief y  cojitrasted — As 
to  whether  natural  or  supernatural — ^As  to  variability,  definite 
or  indefinite — As  to  change  from  one  species  to  another  by 
transmutation  or  substitution — As  to  universality  of  law  of  con- 
tinuity       29 

CHAPTER   II. 

THE   RELATION    OF    LOCIS    AGASSIZ    TO    THE    THEORY    OF    EVOLUTION. 

General  misunderstanding  on  this  subject — Necessary  to  give  sketch 
of  history  of  the  idea — Greeks,  Lucretius,  Swedenborg,  and 
Kant — First  scientific  presentation  by  Lamarck — General  char- 
acter of  Lamarck's  views — Failed,  and  rightly  so — Next,  Cham- 
bers's "Vestiges  of  Creation" — Its  general  character — Failed, 
and  rightly  so — Some  think  this  unfortunate — Why  not  so — 
An  obstacle  must  be  removed  and  a  basis  laid  .         .         .         .82 

The  obstacle  removed — Old  views  in  regard  to  forces — Correlation  of 
forces  established — But  vital  force  considered  exception — There- 
fore living  forms  also  supposed  exception  to  mode  of  origin  of 
other  forms — Then  vital  forces  also  correlated — Therefore,  a 
priori  probable  that  living  forms  also  correlated  with  other 
forms  as  to  mode  of  origin — Thus  obstacle  removed  .         .         .35 


CONTENTS.  yii 

PAGE 

The  basis  laid — Agassiz  laid  inductive  basis  of  evolution,  although  he 
refused  to  build — He  established  the  laws  of  evolution  and  per- 
fected the  method  of  comparison — Importance  of  method  dis- 
cussed— The  method  of  flotation — The  method  of  experiment — 
The  difficulty  of  applying  these  to  life  phenomena — Method  of 
comparison  shown — (1)  In  Taxonomic  series — (2)  In  Ontogcnic 
series — (3)  In  Phylogenic  series — Cuvier  the  great  worker  by 
comparison  in  the  Taxonomic  series — Agassiz  in  the  Ontogenic 
and  Phylogenic — Agassiz  also  established  the  three  laws  of  evo- 
lution given  in  previous  chapter — Thus  he  laid  foundation — 
Why  he  did  not  build — Supposed  identity  of  evolution  and  ma- 
terialism— The  obstacle  being  removed  and  the  basis  laid,  when 
evolution  again  brought  forward  it  was  universally  accepted, 
because  the  world  was  prepared — Place  of  Agassiz  and  Darwin 
compared — Formal  science  vs.  physical  science — Illustrated  by 
relation  of  Kepler  to  Newton — Relation  of  Agassiz  to  time  cos- 
mos similar  to  that  of  Kepler  to  space  cosmos — So  Darwin  to 
Newton — Some  reflections  on  the  above — Gravitation  is  the  law 
of  space  cosmos — Evolution  of  time  cosmos — Of  the  divine 
spheral  music  gravitation  is  the  chordal  harmony  and  evolution 
the  melody 37 


PAKT   II. 

EVIDENCES  OF  THE  TEETH  OF  EYOLETIOK 

CHAPTER  I. 

GENERAL    EVIDENCES    OF   EVOLUTION    AS   A   UNIVERSAL   LAW. 

Evolution  is  continuity,  causal  relation,  gradual  Seeomin^'— Increasing 
acceptance  of  this  idea— First  accepted  for  inorganic  forms, 
mountains,  continents  and  seas,  rocks  and  soils,  earth  as  a 
whole,  heavenly  bodies— Therefore  acknowledged  for  all  inor- 
ganics—Influence of  geology  in  bringing  about  this  change- 
Organic  forms:  acknowledged  for  individuals,  true  for  classes, 
orders,  families,  genera— Races  and  varieties  also  formed  gradu- 
ally—Artificial species  formed  gradually— Examples  of  gradual 
changes  in  wild  species— Hyatt's  researches— Other  examples 
—Summing  up  of  general  evidence— Sufficient  ground  for  indue- 


viii  CONTENTS. 

PAGE 

tion — But  evolution  is  not  only  inductively  probable  but  certain, 
axiomatic — It  is  the  law  of  causation  applied  to  forms,  and 
therefore  a  necessary  truth        .         .         .         .         .         .         .53 

CHAPTER  II. 

SPECIAL   PROOFS    OF   EVOLUTION. 

Introductory. 

Special  proofs  necessary — Evolution,  though  certain,  is  not  yet  ac- 
cepted by  the  popular  mind — Different  departments  from  which 
proofs  are  drawn      .         .         .         .         .         .         .         .         .67 

Origin  of  new  organic  forms  ;  the  old  view  briefly  stated — Necessary 
to  give  a  brief  statement  of  theories — Old  view — Permanency 
of  specific  types — Supernatural  origin  of  species — Centers  of 
creation — Explanation  of  facts  of  geographical  distribution — 
Of  geological  distribution — Modification  of  extreme  view — 
Variability,  but  within  limits — Illustrated  .         .         .         .68 

The  neio  view  briefly  stated — Indefinite  variability  of  organic  forms — 
Effect  of  environment  on  rigid  forms — On  plastic  forms — Taxo- 
nomic  groups  represent  degrees  of  kinship         .         .         .         .72 

Factors  of  evolution — (1)  Physical  environment — (2)  Use  and  disuse 
of  organs — (3)  Natural  selection — (4)  Sexual  selection — (5)  Physi- 
ological selection — Its  necessity  shown — Its  operation  explained 
— Compared  with  natural  selection — Cause  of  variation  unknown 
— Explanation  of  this  is  the  next  great  step  in  the  theory  of 
evolution ...........     73 

CHAPTER   III. 

SPECIAL    PROOFS    FROM    THE    GENERAL    LAWS    OF   ANIMAL    STRUCTURE,    OR 
COMPARISON    IN    THE    TAXONOMIC    SERIES. 

General  Principles. 

Analogy  and  homology — Defined  and  illustrated  by  examples— Wings 
and  limbs— Lungs,  gradual  formation  of,  traced  in  the  Taxo- 
nomic  series — Traced  in  the  Ontogenic  series — Examples  of 
homology  in  plants :  tuber,  cactus-leaf,  acacia-leaf— Definitions 
repeated  and  further  explained — Common  origin  is  the  only  ex- 
planation of  homology        ....  ...     81 

Primary  divisions  of  the  animal  Tcingdom — True  ground  of  such  divi- 
sions is  ability  to  trace  homology — We  take  examples  only  from 


CONTENTS. 


IX 


PAGE 

vertebrata  and  articulata — Compare  to  styles  of  arcbitecture — 
To  machines — To  branching  stem 89 


CHAPTER   lY. 

PROOFS    FROM   HOMOLOGIES    OF   THE    VERTEBRATE    SKELETON. 

Common  general  plan — In  several  respects — Strongly  suggestive 
of  common  origin — Details  of  structure  demonstrative  of  the 
same 93 

Special  homology  of  vertebrate  limbs  .         .         .         .         .         .95 

Fore-limbs — Comparison  of  fore-limbs  of  mammals,  birds,  reptiles, 
and  fishes,  part  for  part — Gradual  changes  in  collar-bone  and 
coracoid — In  position  of  elbow — In  bones  of  forearm — In  posi- 
tion of  wrist — In  the  tread — The  term  manus — Number  of  toes 
— Modifications  for  flight  in  various  animals — For  swimming  in 
■whales  and  fishes 95 

Hind-limbs — Comparison  of  hind-limbs  of  several  mammals — Posi- 
tion of  knee — Of  heel — Plantigrade  and  digitigrade — Degrees 
of  the  latter — Number  of  toes — General  law  in  regard  to  num- 
ber of  similar  parts — Order  of  toe-dropping  in  artiodactyles — 
In  perissodactyles     .........  103 

Genesis  of  the  horse — Changes  in  foot-structure — Same  true  of  other 
parts  of  skeleton — Only  natural  explanation  is  derivation — Na- 
ture compared  with  man  in  mode  of  working — Angels — Griffins 
— Centaurs — Muscular  and  nervous  systems — Visceral  organs   .  108 

CHAPTER  V. 

HOMOLOGIES    OF   THE    ARTICULATE    SKELETON. 

Illustrations  from  this  type — Plan  of  structure  entirely  different 
—  General  plan  of  structure  explained  and  modifications 
shown  —  Shrimp  —  Modification  of  segments  and  of  append- 
ages for  various  purposes :  swimming,  walking,  eating,  sense — 
Illustrated  by  other  crustaceans — By  myriapods — By  marine 
worms — Crabs — Embryonic  development  of  crabs — Insects — 
Modification  of  segments  and  appendages — Mouth  parts  of  in- 
sects          11"^ 

Illustration  of  the  law  of  (?^;^er(?w^^«^^(»^— Cells— Segments— Individ- 
uals— Homologies  in  other  departments  of  animals,  but  these 


X  CONTENTS. 


PAGE 


are  less  familiar — Between  primary  groups,  homology  untrace- 
able in  adult  forms — But  these  also  probably  connected  by  com- 
mon origin — Different  views  as  to  origin  of  vertebrates     .         .126 

CHAPTER  YI. 

PROOFS   FROM   EMBRYOLOGY,    OR    COMPARISON    IN    THE    ONTOGENIC   SERIES. 

Resemblance  of  the  three  series — Frog,  in  Ontogeny  passes  through 
main  stages  of  Taxonomy  and  Phylogeny — Resemblance  only 
general — Many  steps  dropped  out  in  Ontogeny  .         .         .         .130 

(1)  Ontogeny  of  tailless  amphibians — The  frog :  fish  stage,  perenni- 

branch  stage,  caducibranch  stage,  anoural  stage — Same  stages 

in  Phylogeny 132 

(2)  Aortic  arches — Those  of  lizard  described — Origin  from  gill-arches 

of  fish — Change  from  one  to  the  other  in  Ontogeny  of  a  frog 
— Same  changes  in  Phylogeny  of  lizard — Embryonic  condition 
of  mammalian  heart  and  vessels — Gradual  change  and  final  con- 
dition in  birds — In  mammals — Gradual  decrease  in  number  of 
aortic  arches  as  we  go  up  the  vertebrate  scale — Cogency  of  the 
argument  from  aortic  arches     .         .         .         .         .         .         .132 

(3)  Vertebrate  brain — Fish  brain — Brain  of  reptiles,  birds,  mammals, 

man  compared — Human  brain  passes  through  similar  stages — 
Changes  in  complexity  of  structure  in  Taxonomy — Same  changes 
in  Ontogeny  of  mammals — Same  in  Phylogeny  of  reptiles,  birds, 
mammals  ...........   144 

Cephalization — Explanation  of,  in  body,  in  mind       .         .         ,         .153 

(4)  Fish-tails — Homocercal  and  heterocercal — Vertebrated  and  non- 

vertebrated — Order  of  change  in  Ontogeny — Same  in  Phylogeny 
— Similar  changes  in  birds'  tails  in  Ontogeny  and  Phylogeny — 
In  other  tailless  animals — Examples  from  articulates,  insects, 
crustaceans,  etc 154 

Illustration  of  the  differentiation  of  the  whole  animal  kingdom — De- 
velopment of  eggs  of  all  kinds  of  animals — This  a  type  of 
changes  in  Phylogeny — Why  Ontogeny  repeats  Phylogeny — Law 
of  acceleration  ..........   158 

Proofs  from  rudimentary  and  useless  organs — Examples  from  whale : 
Teeth — Limbs — Hair — Olfactlve  organs — Examples  from  man : 
muscles,  caecal  appendage — Significance  of  useless  organs  .  161 


CONTENTS.  xi 


CHAPTER  VII. 

PROOFS    FROM    GEOGRAPHICAL    DISTRIBUTION    OF   ORGANISMS. 

PAGE 

GeograpJiical  foMnas  and  floras — Conditions  which  limit .         .         .165 

Temperature-regions — Illustrated  by  plants — In  latitude  and  in  ele- 
vation— Same  in  animal  species 166 

More  perfect  definition  of  regions — Range  of  different  Taxonomic 
groups — Gradual  shadings  on  borders  of  range — Shadings  out 
of  individuals  in  number  and  vigor,  but  not  in  specific  character 
— As  if  centers  of  origin — Effect  of  east  and  west  barriers — 
Temperature  regions  repeated  south  of  the  equator,  but  not 
species — As  if  centers  of  origin 168 

Continental  faunas  and  floras — Temperature  zones  continuous,  but 
not  species — Reason :  ocean  barriers — As  if  centers  of  origin — 
Polar  regions :  one.  Why — Temperate  zone — Different  species 
in  different  continents — Species  of  United  States  and  of  Europe 
almost  wholly  different — As  if  origin  local — Exceptions — (1) 
Introduced  species — (2)  Hardy  or  else  wide-migrating  species — 
(3)  Alpine  species — Tropical  zone  of  two  continents  still  more 
different — Same  true  of  south  temperate  zone   .         .         .         .170 

SicbdlvLsions  of  continental  faunas  and  floras — Illustrated  by  fauna 

and  flora  of  United  States  .         .         .         .         .         .         .  1*73 

Specicd  cases — Australia — Madagascar — Galapagos — River  mussels  .  174 

Marine  species  —  Same  principles  applicable  —  Therefore  organic 
forms  grouped  in  regions,  sub-regions,  provinces,  etc. — Primary 
regions  according  to  Wallace — According  to  Allen    .         .         .  1 74 

Theory  of  the  origin  of  geographical  diversity — Specific  centers  of 
creation — Objections  to.  The  element  of  time  left  out — Pro- 
gressive change  in  unlimited  time,  or  evolution  the  only  rational 
explanation — This  connects  with  geographical  changes  in  geo- 
logical times,  especially  the  Glacial  epoch — Geographical  diver- 
sity in  other  times     .         .         .         .         .         .         .         .         .175 

Most  probable  vieio  of  the  general  process — Last  great  period  of 
change  was  the  Glacial  epoch — This,  therefore,  is  the  key  to 
geographical  distribution— Condition  of  things  during  the  Glacial 
epoch — In  'America — Changes  in  temperature — In  physical  geog- 
raphy and  in  species— In  Europe — Application  of  principles      .  1 78 

(1)  Australia — Characteristics  of  its  fauna — Explanation  of— Isola- 
tion very  early — Position  of  marsupials  and  monotremcs  in  the 


xii  CONTENTS. 

PAGE 

Taxonomic  scale — Australia  isolated  before  the  Tertiary — Effect 

of  competition  on  evolution       .         .         .         .         .         .         .182 

(2)  Africa — African  region  defined — Two  groups  of  its  mammals, 

indigenes  and  invaders — Effect  of  the  invasion  .         .  .186 

(3)  Madagascar — Characteristics  of  its  fauna — Relation  to  African 

indigenes — Separated  before  the  invasion— Significance  of  its 
lemurs       ...........  187 

(4)  Islcnid  life — Two  kinds  of  islands — Defined  and  illustrated  by  ex- 

amples— (a)  Continental  islands — General  character  of  fauna — 
Illustrated  by  Madagascar,  New  Zealand,  British  Islands,  coast 
islands  of  California — Characteristics  of  the  faunas  of  these 
explained  —  (6)  Oceanic  islands  —  Defined  —  Characteristics  of 
faunas  and  their  origin 189 

(5)  Alpine  species — Characteristics  of  and  their  origin  explained — 

Migrations  of  Arctic  species  during  Glacial  times,  and  their  iso- 
lation on  mountains  .         .         .         .         .         .         .         .197 

Objection — Mode  of  change  of  species  on  borders  of  ranges — Exam- 
ples— Sweet-gum — Sequoia        .         .         .         .         .         .         .199 

Answer — Distribution  of  these  forms  in  time,  and  their  migrations — 

They  are  remnants — Intermediate  forms  are  extinct  .         .         .  !i01 

CHAPTER  VIII. 

PROOFS    FROM    ARTIFICIAL    PRODUCTION    OF   VARIETIES,   RACES,    SPECIES,    ETC, 

Limitation  of  the  use  of  experiment  in  morphology — Unconscious  ex- 
periments in  breeding,  and  their  results — Principles  involved — 
Inheritance,  immediate  and  ancestral — Effect  of  true  breeding 
long  continued — Method  of  selection  illustrated  by  diagram — 
Formation  of  a  race — Process  the  same  in  nature — Show^  select- 
ive effect  of  physical  environment — Of  organic  environment — 
Of  migrations — Of  unlimited  time — Other  factors  of  change, 
and  their  effects  shown  in  nature  and  in  domestication — Differ- 
ences between  artificial  and  natural  species        ....  204 

First  difference^  reversion — The  tendency  to  reversion  described — 

The  reason  explained — Illustrated  by  the  case  of  the  pointer     .  211 

Second  difference^  intermediate  forms — Reason  is,  these  are  elimi- 
nated in  nature  .........  214 

TJiird  difference,  crossfertility — Natural  species  are  usually  cross- 
sterile — Degrees  of  cross-stei-ility — Two  bases  of  species,  mor- 
phological and  physiological — Two  kinds  of  isolation,  sexual 


CONTENTS.  xiii 

PAGE 

repugnance  and  cross-sterility — Latter  most  essential — Illus- 
trated by  plants  and  hermaphrodite  animals — Former  only 
higher  animals — Natural  laws  interfered  with  by  domestication 
— Illustrated  by  plants  and  animals 214 

Law  of  cross-breeding — Effect  of  close  breeding — Of  crossing  varieties 
to  a  limit — The  law  investigated — Reproduction  in  lowest  organ- 
isms— Fission — Gemmation — Internal  gemmation — Sex  intro- 
duced— Effect  of,  is  funding  of  differences  in  offspring  and  ten- 
dency to  variation — Sexual  and  non-sexual  reproduction  com- 
pared— Separation  of  sex  elements — Of  sex-individuals — Intro-  ' 
duction  of  sex-attraction — Funding  of  greater  differences  in 
offspring — Crossing  of  varieties — Diagram  illustrating  effect  in 
vigor — Effect  also  in  plasticity — Application  of  these  principles 
— Necessity  of  sexual  isolation  to  produce  species — Origin  of 
cross-sterility  and  thus  of  species  by  Dr.  Romanes's  idea — Why 
artificial  varieties  are  cross-fertile — Geographical  species  some- 
times cross-fertile — Application  of  principles — Absence  of  inter- 
mediate links  in  natural  species  explained — Under  what  condi- 
tions such  are  found — Further  explanation  of  this  point — 
Illustrated  by  a  growing  tree 218 

Objection  answered — Intermediate  links  ought  to  be  found  fossil — 
Answer  (1)  Imperfection  of  record.  (2)  The  term  species  in- 
definite. (3)  Transitions  between  all  other  taxonoraic  groups 
abundant.  (4)  Between  species,  also,  both  living  and  fossil— 
Of  fossil,  Planorbis  of  Steinheim— Other  examples— (5)  Why 
transition-forms  are  rare-Answer— Changes  in  every  depart- 
ment of  nature  are  paroxysmal— Illustrated— So  the  steps  of 
evolution  paroxysmal— Critical  periods  in  evolution— Causes  of 
rapid  advance— Apparent  discontinuity  between  species— (1) 
changes  paroxysmal,  (2)  Brooks's  idea— Male  sex  is  the  pro- 
gressive element— Illustrated  by  society— Effect  of  prosperous 
times— Mrs.  Treat's  experiments— Hard  times  produce  excess 
of  males,  and  therefore  tend  to  diversity— Summary  .         .  230 

Objection— EsYVt\a.n  drawings  and  mummy  plants,  show  no  change 
—Answer  (1)  Time  too  short.  (2)  We  are  now  in  time  of  slow 
change.  (3)  All  species  don't  change,  most  become  extinct.  (4) 
Evolution  is  probably  slower  now  than  formerly— Reasons  for 
so  thinkini^— Organic  evolution  approaching  completion— Other 
supposed  objections 


xiv  CONTEXTS. 

PAGE 

Origin  of  heaniy — Explanation  of,  in  higher  animals — In  flowering 

plants — But  in  many  eases  we  can't  explain       .         .         .         .251 

Incipient  organs — DiflSculty  of  explaining — But  these  are  not  objec- 
tions to  the  fact  of  evolution,  but  only  to  the  sufficiency  of  the 
present  theories  of  evolution.  Therefore,  all  discussion  concerns 
special  theories.     The  fact  of  evolution  is  certain       .         .         .  252 


PAKT   III. 

THE  RELATION  OF  EVOLUTION  TO  RELIGIOUS 

THOUGHT. 

CHATTER    I. 

INTRODUCTORY. 

Evolution  if  true  affrcts  every  department  of  thought — What  will  be 
its  effect  on  religious  beliefs  ? — Objection  that  truth-seeker  has 
nothing  to  do  with  effects — Answered        .....  257 

Relation  of  the  true  and  the  good       .         .         .         .         .         .         .259 

Relation  of  philosophy  to  life — The  three  necessary  elements  of  a 
rational  philosophy — Application  to  the  case  in  hand — And  the 
subject  of  Pai't  III  justified — Exaggerated  fears — Different  forms 
of  the  conflict  of  science  and  religion — 1,  Heliocentric  theory 
— First  effect  and  final  result — 2,  Law  of  gravitation — Effect 
and  result — 3,  Antiquity  of  the  earth  and  cosmos — Effect  and 
result — 4,  Antiquity  of  man — 5,  Evolution        ....  259 

CHAPTER   II. 

THE    RELATION    OF    EVOLUTION    TO    MATERIALISM. 

Supposed  identity — Tendency  of  the  age — Evolution  does  not  differ  in 
this  regard  from  other  laws  of  Nature— Absurdity  of  identifica- 
tion illustrated  in  many  ways— 1,  Effect  of  discovery  of  process 
of  making— 2,  Effect  of  new.  form  of  old  truth— 3,  Planner  in 
which  vexed  questions  are  settled  and  rational  philosophy 
found — Illustrated — A  true  philosophy  is  a  reconciliation  of 
partial  views— Three  possible  views  of  origin  of  individuals 
and  of  species ;  two  one-sided  and  partial,  and  the  third,  com- 


CONTENTS.  XV 

PAGE 

bining,  reconciling,  and  therefore  rational — The  only  bar  to 
speedy  reconciliation  is  dogmatism — Theological  and  scientific — 
The  appropriate  rebuke  for  each — Therefore  evolution  does  not 
differ  from  other  laws  in  regard  to  its  relation  to  materiahsm — 
Nevertheless,  great  changes  in  our  traditional  beliefs  impending 
— Main  changes  are  notions  concerning  God,  Nature,  and  man, 
in  their  relations  to  one  another 266 

CHAPTER   III. 

THE  RELATION  OF  GOD  TO  NATURE. 

The  issue  in  regard  to  this  relation  stated — The  growth  of  the  issue 
described — The  old  view  of  direct  relation — The  effect  of  science 
and  the  resulting  view — The  compromise — Destroyed  by  evolu- 
tion— The  issue  forced — The  alternative  view — Immanence  of 
Deity — This  view  explained — Objection  of  idealism — Answered 
— It  is  not  subjective  idealism — Objection  of  pantheism — An- 
swer deferred — Objection  that  the  view  is  incompatible  with 
practical  Hfe — Answered 279 

CHAPTER    lY. 

THE    RELATION   OF   MAN    TO    NATURE. 

Tlie  txoo  extreme  vieios  in  this  regard — They  are  views  from  different 
points,  psychical  and  material — The  latter  very  productive  in 
modern  times — But  many  fear  the  final  effect — Reconciliation  is 
possible — Scientific  materialism  has  two  branches — Physiologi- 
cal branch  explained — Conclusion — Answer — Relation  of  psychic 
to  brain  changes  is  inscrutable — The  mystery  illustrated — Out- 
side and  inside  view — Different  from  other  phenomena  in  this 
regard 286 

Evolution  branch — Close  relation  of  man  to  animals — Therefore  must 
extend  immortal  spirit  to  animals — to  plants — to  all  existence, 
and  thus  identify  immortality  with  conservation  of  force — Em- 
bryonic series — Where  did  spirit  enter  ? — Evolution  series — 
Where  did  spirit  enter  ? — Answer — Derived  from  Nature — The 
true  view  of  ori2:in  stated — Show  that  it  is  not  in  discord  with 
other  phenomena  of  evolution — The  five  planes  of  matter  and  of 
force — The  change  from  one  to  another  not  gradual  now  nor  in 


xvi  CONTENTS. 

PAOK 

the  evolution  of  natural  forces — Consecutive  births  into  higher 
forms — Relation  of  these  facts  to  immortaUty — The  process 
briefly  stated — Omnipresent  divine  energy  individuated  to  sepa- 
rate entity  in  man — Anima  of  animals  is  spirit  in  embryo — Came 
to  birth  in  man — Illustrated  in  other  ways — By  submergence  and 
emergence — By  planet  birth — By  physical  birth — By  grades  of 
organic  individuality — So  also  spirit -individuality — Any  animal 
conscious  of  self  would  be  immortal — Similar  changes  in  pass- 
ing from  animals  to  man  in  all  other  departments  of  psychic 

activity 293 

Some  general  conclusions — (1),  Two  series  of  changes,  brain  changes 
and  mind  changes — The  initiative  in  animals — In  man — (2), 
Justification  of  term  ^^  vital  principle^'' — Becomes  entity  in  man 
— (3),  This  view  is  a  complete  reconciliation  of  realism  and 
nominalism — (4),  No  meaning  in  Nature  without  spirit — And  no 
meaning  in  geological  history  without  derivative  origin  of  spirit 
— Material  evolution  finds  its  goal  in  man,  psychic  evolution  in 
the  divine  man 304 

CHABTER  V. 

THE   RELATIOX   OF   GOD   TO    MAN. 

Question  of  revelation — Difficulty  of  the  subject — Operation  of  divine 
spirit  on  spirit  of  man  more  direct  than  on  Nature — This  is  reve- 
lation— This  is  no  violation  of  law,  but  operation  by  higher  law 
— Term  supernatural  is  relative — Illustrated — There  is  but  one 
kind  of  revelation,  and  this  to  all  men  in  different  degrees — 
Always  imperfect,  and  therefore  must  be  tried  by  reason  .         .  308 

CHAPTER  VI. 

THE   OBJECTION,    THAT   THE    ABOVE    VIEW    IMPLIES    PANTHEISM,    ANSWERED. 

77ie  objection  stated  and  the  general  answer — In  deepest  questions 
single  lines  of  thought  lead  to  extreme  views — Must  follow  other 
lines — These  lead  to  personality 312 

(1)  Exact  character  of  relation  of  God  and  of  necessary  law  to  man's 

freedom  is  inscrutable        .         .         .         .         .         .         .         .315 

(2)  On  the  inside  of  brain-changes  we  find  personality — So  on  the  in- 

side of  natural  phenomena  must  also  be  person — In  either  case 


CONTEXTS.  xvii 


\ 


PAGE 

science  studies  the  outside  only — In  Nature  all  is  mechanics  on 
the  outside,  but  all  is  mind  on  inside — Thought  behind  brain 
changes  compels  behef  in  same  behind  natural  phenomena — 
Law  of  infinite  expansion — Illustrated  by  ideas  of  Space  and 
Time — So  also  with  idea  of  self — Infinite  person  inconceivable, 
but  contrary  is  more  inconceivable — Illustrated  by  ideas  of  Space 
and  Time 315 

(3)  Idea  of  Causatioji  and  of  Force — Derived  from  ivithin — Steps  of 

the  evolution  of  this  idea — Final  result  is  one  infinite  personal 
.     will — Expansion  of  idea  of  causal  nexus  between  phenomena  to 
the  idea  of  one  infinite  cause 319 

(4)  Idea  of  design  also  originates  within — Ineradicable,  but  changes 

form — Expands  to  infinity — Same  change  produced  by  science 
in  all  our  notions  concerning  God — Same  in  our  sense  of  inys- 
tery — Same  in  our  notions  concerning  creation — Same  in  our 
conceptions  of  design — Thus,  self-consciousness  behind  brain- 
changes  compels  belief  in  God  behind  Nature — The  closeness  of 
connection  in  the  one  case  necessitates  closeness  of  connection 
in  the  other — Every  material  change  in  Nature  caused  by  a  men- 
tal change  behind  Nature 322 


"D" 


CHAPTER   YII. 

THE   RELATION    OF    EVOLUTION    TO    THE    PROBLEM    OP   EVIL. 

The  difficulty  of  the  problem — The  light  on  it  by  evolution — Evil 
must  be  based  on  the  constitution  of  Nature  and  therefore  uni- 
versal— Some  of  its  forms 328 

(1)  Physical  evil  in  animal  Jciyigdom — Condition  of  organic  evolu- 

tion is  struggle  with  an  apparently  inimical  environment — 
In  its  course  it  seems  evil — Looking  back  from  the  end  it  is 
good 328 

(2)  Physical  evil  in  relcdion  to  man — Necessary  condition  of  social 

evolution  is  also  struggle  with  a  seeming  evil  environment — But 
looking  back  from  the  end  this  evil  is  also  seen  to  be  good — 
Without  it  man  would  never  have  emerged  from  animality         .  329 

(3)  Organic  evil — Disease — This  also  is  the  necessary  condition  of  ac- 

quisition of  knowledge  of  organic  Nature — In  the  course  of  evo- 
lution it  seems  evil,  but  from  the  end  it  is  seen  to  be  good — In 
the  physical  world  laws  of  Nature  are  beneficent  in  their  general 


xviii  CONTENTS. 

PAGE 

operation,  and  only  evil  in  their  specific  operation  through  our 
ignorance ...........  330 

(4)  Moral  evil — Moral  disease — Difference  between  this  and  other 
forms  of  evil — Can  this  also  be  transmuted  into  good  ? — This  is 
only  the  highest  form  of  evil,  and  therefore  subject  to  the  same 
laws  of  evolution — Here  also  elevation  comes  only  through 
knowledge  and  power,  and  these  only  through  struggle  with  ap- 
parent evil — In  course  it  seems  evil,  looking  back  from  end  it 
is  seen  to  be  good  to  the  race — In  all,  therefore,  the  individual 
is  sacrificed  to  the  race,  but  impossible  here — A  way  of  escape 
found  in  the  nature  of  a  moral  being — In  this  case  not  only 
final  victory  for  the  race,  but  also  within  the  power  of  the  in- 
dividual— In  this  case  success  is  in  proportion  to  honest  effort 
in  right  spirit — Roots  of  evil  in  the  necessary  law  of  evolution 
— It  is  the  necessary  condition  of  all  progress — Without  it  a 
moral  being  is  impossible — From  philosophic  point  of  view 
things  are  not  good  and  evil,  but  only  higher  and  lower — ^All 
things  good  in  their  places — Evil  is  discord — Good  is  due  rela- 
tion— Action  and  reaction  of  higher  and  lower  is  the  necessary 
condition  of  true  virtue 382 


PAET    I. 
WHAT  IS  EVOLUTION? 


CHAPTER  I. 

ITS   SCOPE   AKD   DEFII^ITION^. 

A  Type  of  Evolution. — Every  one  is  familiar  with 
the  main  facts  connected  with  the  development  of  an 
egg.  We  all  know  that  it  begins  as  a  microscopic  germ- 
cell,  then  grows  into  an  egg,  then  organizes  into  a  chick, 
and  finally  grows  into  a  cock ;  and  that  the  whole  pro- 
cess follows  some  general,  well -recognized  law.  Now, 
this  process  is  evolution.  It  is  more — it  is  the  type  of 
all  evolution.  It  is  that  from  which  we  get  our  idea  of 
evolution,  and  without  which  there  would  be  no  such 
word.  Whenever  and  wherever  we  find  a  process  of 
change  more  or  less  resembling  this,  and  following  laws 
similar  to  those  determining  the  development  of  an  egg, 
we  call  it  evolution. 

Universality  of  Evolution. — Evolution  as  a  process  is 
not  confined  to  one  thing,  the  egg,  nor  as  a  doctrine  is 
it  confined  to  one  department  of  science — biology.  The 
process  pervades  the  whole  universe,  and  the  doctrine 
concerns  alike  every  department  of  science — yea,  every 
department  of  human  thought.  It  is  literally  one  half 
of  all  science.     Therefore,  its  truth  or  falseness,  its  ac- 


4  WHAT  IS  EVOLUTION? 

ceptance  or  rejection,  is  no  trifling  matter,  affecting  only 
one  small  corner  of  the  thought-realm.  On  the  con- 
trary, it  affects  profoundly  the  foundations  of  philos- 
ophy, and  therefore  the  whole  domain  of  thought.  It 
determines  the  whole  attitude  of  the  mind  toward  Na- 
ture and  God. 

I  have  said  evolution  constitutes  one  half  of  all  sci- 
ence. This  may  seem  to  some  a  startling  proposition.  I 
stop  to  make  it  good. 

Every  system  of  correlated  parts  may  be  studied  from 
two  points  of  view,  which  give  rise  to  two  departments 
of  science,  one  of  which — and  the  greater,  and  more  com- 
plex— is  evolution.  The  one  concerns  changes  within 
the  system  by  action  and  reaction  between  the  parts, 
producing  equilibrium  and  stability  ;  the  other  concerns 
the  progressive  movement  of  the  S3^stem,  as  a  whole,  to 
higher  and  higher  conditions  —  the  movement  of  the 
point  of  equilibrium  itself,  by  constant  slight  disturb- 
ance and  readjustment  of  parts  on  a  higher  plane,  with 
more  complex  inter-relations.  The  one  concerns  the 
laws  of  sustentation  of  the  system,  the  other  the  laws 
of  evolution.  The  one  concerns  things  as  they  are,  the 
other  the  process  by  which  they  become  so.  Now,  Nature 
as  a  whole  is  such  a  system  of  correlated  parts.  Every 
department  and  sub-department  of  Nature,  whether  it  be 
the  solar  system  or  the  earth,  or  the  organic  kingdom,  or 
human  society,  or  the  human  body,  is  such  a  system  of 
correlated  parts,  and  is  therefore  subject  to  evolution. 
We  can  best  make  this  thought  clear  by  examples : 


ITS   SCOPE   AND   DEFINITION.  5 

1.  Take,  then,  the  human  hody.  This  complex  and 
beautiful  system  of  correlated  and  nicely-adjusted  parts 
may  be  studied  in  a  state  of  maturity  and  equilibrium, 
in  which  all  the  organs  and  functions  by  action  and 
reaction  co-operate  to  produce  perfect  stability,  health, 
and  physical  happiness.  This  study  is  physiology.  Or 
else  the  same  may  be  studied  in  a  state  of  progressive 
change.  Now,  we  perceiye  that  the  stability  is  never 
perfect — the  point  of  equilibrium  is  ever  moving.  By 
the  ever-changing  number  and  relative  power  of  the  co- 
operating parts  the  equilibrium  is  ever  being  disturbed, 
only  to  be  readjusted  on  a  higher  plane,  with  still  more 
beautiful  and  complex  inter-relations.  This  is  growth, 
development,  evolution.  Its  study  is  called  embryology. 
2.  Take  another  example  —  the  solar  system.  We  may 
study  sun,  planets,  and  satellites  in  their  mutual  actions 
and  reactions,  co-operating  to  j^roduce  perfect  equilib- 
rium, stability,  beautiful  order,  and  musical  harmony. 
This  is  the  ideal  of  physical  astronomy  as  embodied  in 
Laplace's  ^'^Mecanique  Celeste."  Or  we  may  study  the 
same  in  its  origin  and  progressive  change.  Now,  we  per- 
ceive that  equilibrium  and  stability  are  never  absolutely 
perfect,  but,  on  the  contrary,  there  is  continual  disturb- 
ance with  readjustment  on  a  higher  plane — continual  in- 
troduction of  infinitesimal  discord,  only  to  enhance  the 
grandeur  and  complexity  of  the  harmonic  relatk)ns. 
This  is  the  nebular  hypothesis — the  theory  of  the  devel- 
opment of  the  solar  system.  It  is  cosmogony  ;  it  is  evo- 
lution.    3.  Again  :  society  may  be  studied  in  the  mutual 


6  WHAT  IS  EVOLUTION? 

play  of  all  its  social  functions  so  adjusted  as  to  produce 
social  equilibrium,  happiness,  prosperity,  and  good  gov- 
ernment. This  is  social  statics.  But  equilibrium  and 
stability  are  never  perfect.  Permanent  social  equilibri- 
um would  be  social  stagnation  and  decay.  Therefore,  we 
must  study  society  also  in  its  onward  movement — the 
equilibrium  ever  disturbed,  only  to  be  readjusted  on  a 
higher  plane  with  more  and  more  complexly  inter-related 
parts.  This  is  dynamics — social  progress.  It  is  evolu- 
tion. 4.  Again :  the  earth,  as  a  w^hole,  may  be  studied 
in  its  present  forms,  and  the  mutual  action  of  all  its  parts 
— lands  and  seas,  mountains  and  valleys,  rivers,  gulfs, 
and  bays,  currents  of*  air  and  ocean — and  the  manner  in 
which  all  these,  by  action  and  reaction,  co-operate  to  pro- 
duce climates  and  physical  conditions  such  as  we  now 
find  them.  This  is  physical  geography.  Or,  we  may 
study  the  earth  in  its  gradual  progress  toward  its  pres- 
ent condition — the  changes  which  have  taken  place  in 
all  these  parts,  and  consequent  changes  in  climate  ;  in  a 
word,  the  gradual  process  of  becoming  what  it  now  is. 
This  is  physical  geology — it  is  evolution.  5.  Lastly,  we 
may  study  the  whole  organic  Tcingdom  in  its  entirety 
as  we  now  find  it — the  mutual  relation  of  different 
classes,  orders,  genera,  and  species  to  each  other  and  to 
external  conditions,  and  the  action  and  reaction  of  these 
in  the  struggle  for  life — the  geographical  distribution  of 
species  and  their  relation  to  climate  and  other  physical 
conditions,  the  whole  constituting  a  complexly  adjusted 
and  permanent  equilibrium.     This  is  a  science  of  great 


ITS   SCOPE   AND   DEFINITION.  7 

importance,  but  one  not  yet  distinctly  conceived,  much 
less  named.*  Or,  we  may  study  the  same  in  its  gradual 
]3rogTessive  approach,  throughout  all  geological  times, 
toward  the  present  condition  of  things,  by  continual 
changes  in  the  parts,  and  therefore  disturbance  of  equi- 
librium and  readjustment  on  a  higher  plane  with  more 
complex  inter-relations.  This  is  development  of  the 
organic  kingdom.  In  the  popular  mind  it  is,  par  excel- 
lence, evolution. 

"VVe  might  multiply  examj^les  without  limit.  There 
are  the  same  two  points  of  view  on  all  subjects.  As 
already  said,  in  the  one  we  are  concerned  with  things 
as  they  are  ;  in  the  other,  with  ftie  process  by  which 
they  became  so.  This  ^Maw  of  becoming"  in  all  things 
— this  universal  law  of  progressive  inter-connected  change 
— may  be  called  the  law  of  continuity.  We  all  recog- 
nize the  universal  relation  of  things,  gravitative  or 
other,  in  space.  This  asserts  the  universal  causal  rela- 
tion of  things  in  time.  This  is  the  universal  law  of 
evolution. 

But  it  has  so  happened  that  in  the  popular  mind  the 
term  evolution  is  mostly  confined  to  the  development  of 
the  organic  kingdom,  or  the  law  of  continuity  as  applied 
to  this  department  of  Nature.  The  reason  of  this  is  that 
this  department  was  the  last  to  acknowledge  the  suprem- 
acy of  this  law ;  this  is  the  domain  in  which  the  advo- 
cates of  supernaturalism  in    the  realm   of   Nature   had 


*  The  term  Chorology,  used  by  Haeckel,  nearly  covers  the  ground. 
2 


8  WHAT   IS  EVOLUTION? 

made  their  last  stand.  But  it  is  wholly  unphilosoj^hical 
thus  to  limit  the  term.  If  there  be  any  evolution,  'par 
excellence,  it  is  evolution  of  the  individual  or  embryonic 
development.  This  is  the  clearest,  the  most  familiar, 
and  most  easily  understood,  and  therefore  the  type  of 
evolution.  We  first  take  our  idea  of  evolution  from  this 
form,  and  then  extend  it  to  other  forms  of  continuous 
change  following  a  similar  law.  But,  since  the  popular 
mind  limits  the  term  to  development  of  the  organic 
kingdom,  and  since,  moreover,  this  is  now  the  battle- 
ground between  the  advocates  of  continuity  and  discon- 
tinuity— of  naturalism  and  supernaturalism  in  the  realm 
of  Nature — what  we  shall  say  will  have  reference  chiefly 
to  this  department,  though  we  shall  illustrate  freely  by 
reference  to  other  forms  of  evolution. 

Definition  of  Evolution. 

Evolution  is  (1)  continuous  progressive  change,  (2) 
according  to  certain  laws,  (3)  and  by  means  of  resident 
forces.  It  may  doubtless  be  defined  in  other  and  per- 
haps better  terms,  but  this  suits  our  purposes  best. 
Embryonic  development  is  the  tyi3e  of  evolution.  It 
will  be  admitted  that  this  definition  is  completely  real- 
ized in  this  process.  The  change  here  is  certainly  con- 
tinuously progressive  ;  it  is  according  to  certain  well- 
ascertained  laws  ;  it  is  by  forces  (vital  forces)  resident 
in  the  Qgg  itself.  Is,  then,  the  process  of  change  in 
the  organic  kingdom  throughout  geologic  times  like 
this?      Does    it    correspond    to    the    definition    given 


ITS  SCOPE   AND   DEFINITION".  9 

above  ?  Does  it  also  deserve  the  name  of  evolution  ? 
We  shall  see. 

I.  Progressive  Change. — Every  individual  animal  body 
— say  man's — has  become  what  it  now  is  by  a  gradual 
process.  Commencing  as  a  microscopic  spherule  of  liv- 
ing but  apparently  unorganized  proto2:>lasm,  it  gradually 
added  cell  to  cell,  tissue  to  tissue,  organ  to  organ,  and 
function  to  function  ;  thus  becoming  more  and  more 
complex  in  the  mutual  action  of  its  correlated  parts,  as 
it  passed  successively  through  the  stages  of  germ,  egg, 
embryo,  and  infant,  to  maturity.  This  ascending  series 
of  genetically  connected  stages  is  called  the  embryonic  or 
Ontogenic  series.* 

There  is  another  series  the  terms  of  which  are  coex- 
istent, and  which,  therefore,  is  not  in  any  sense  a  genetic 
or  development  series,  but  which  it  is  important  to  men- 
tion, because  to  some  degree  similar  to  and  illustrative  of 
the  last.  Commencing  with  the  lowest  unicelled  micro- 
scopic organisms,  and  passing  up  to  the  animal  scale,  as 
it  noiv  exists,  we  lind  a  series  of  forms  similar,  though 
not  identical,  with  the  last.  Here,  again,  we  find  cell 
added  to  cell,  tissue  to  tissue,  organ  to  organ,  and  func- 
tion to  function,  the  animal  body  becoming  more  and 
more  complex  in  structure,  in  the  mutual  action  of  its 
correlated  parts,  and  the  mutual  action  with  the  environ- 
ment, until  we  reach  the  highest  complexity  of  structure 
and  of  internal  and  external  relations  only  in  the  highest 

• 

*  Ontos-gennao  (individual-making,  or  genesis  of  the  indi'.  idnal). 


10  WHAT   IS  EVOLUTIO:^'? 

animals.  This  ascending  series  may  be  called  the  natural 
history  series  ;  or,  the  classification  or  Taxonomic  series.'^ 
The  terms  of  this  series  are,  of  course,  not  genetically 
connected  ;  at  least,  not  directly  so  connected.  In  what 
way  they  are  connected,  and  how  the  series  comes  to  -be 
similar  to  the  last,  we  shall  see  by-and-by. 

Finally,  there  is  still  a  third  series,  the  grandest  and 
most  fundamental  of  all,  but  only  recently  recognized, 
and  therefore  still  imperfectly  known.  Commencing 
with  the  earliest  organisms,  the  very  dawn  of  life,  in 
the  very  lowest  rocks,  and  passing  onward  and  upward 
through  Eozoic,  Palaeozoic,  Mesozoic,  Cenozoic,  to  the 
Psychozoic  or  present  time,  we  again  find  first  the  lowest 
forms,  and  then  successivelv  forms  more  and  more  com- 
plex  in  structure,  in  the  interaction  of  correlated  parts 
and  in  interaction  with  the  environment,  until  we  reach 
the  most  complex  internal  and  external  relations,  and 
therefore  the  highest  structure  only  in  the  present  time.f 
This  series  we  will  call  the  geological  or  'pliylofjenic  se- 
ries. |  According  to  the  evolution  theory,  the  terms  of 
this  series  also  are  genetically  connected.  It  is,  there- 
fore, an  evolution  series.  Furthermore,  it  is  the  most 
fundamental  of  the  three  series,  because  it  is  the  cause 
of  the  other  two.  The  Ontogenic  series  is  like  it  because 
it  is  a  brief  recapitulation,  through  heredity,  as  it  were 
from  memory,  of  its  main  points.     The  Taxonomic  series 


*  Taxis,  nomos  (relating  to  science  of  arrangement). 

f  This  statement  is  general ;  it  will  be  modified  hereafter. 

X  Phuh-gennao  (kind-making) ;  genesis  of  the  race. 


ITS   SCOPE   AND   DEFINITION.  H 

is  like  it  because  the  rate  of  advance  along  different  lines 
was  different  in  every  degree,  and  therefore  every  stage 
of  the  advance  is  still  represented  in  a  general  way 
among  existing  forms.  Some  of  these  points  will  be  ex- 
plained more  fully  in  future  chapters,  in  connection  with 
the  evidences  of  the  truth  of  evolution. 

It  will  be  admitted,  then,  that  we  find  iwogressive 
chmige  in  organic  forms  throughout  geological  times. 
This  is  the  first  point  in  the  definition  of  evolution. 

II.  Change  according  to  Certain  Laws. — We  have 
shown  continuously  progressive  change  in  organic  forms 
during  the  whole  geologic  history  of  the  earth,  similar 
in  a  general  way  to  that  observed  in  embryonic  develop- 
ment. AYe  wish  now  to  show  that  the  laivs  of  change 
are  similar  in  the  two  cases.  What,  then,  are  the  laws  of 
succession  of  organic  forms  in  geologic  times  ?  I  have 
been  accustomed  to  formulate  them  thus  :  a.  The  law  of 
differentiation  ;  h.  The  law  of  progress  of  the  whole  ;  c. 
The  law  of  cyclical  movement.*  We  will  take  up  these 
and  explain  them  successively,  and  then,  afterward,  show 
that  they  are  also  the  laws  of  embryonic  development, 
and  therefore  the  laws  of  evolution. 

a.  Law  of  Differentiation. — It  is  a  most  significant 
fact,  to  Tvhich  attention  was  first  strongly  directed  by 
Louis  Agassiz,  that  the  earliest  representatives  of  any 
group,  whether  class,  order,  or  family,  were  not  what  we 

*  This  formulation  of  the  laws  of  organic  succession  was  given  by  me 
in  1860,  before  I  knew  anything  of  either  Darwin's  or  Spencer's  evolu- 
tion.    They  were  ray  own  mode  of  formulating  Agassiz's  views. 


12  WHAT   IS  EVOLUTION? 

would  now  call  typical  representatives  of  that  group ; 
but,  on  the  contrary,  they  were,  in  a  wonderful  degree, 
connecting  links  ;  that  is,  that  along  with  their  distinc- 
tive classic,  ordinal,  or  family  characters  they  possessed 
also  other  characters  which  connected  them  closelv  with 
other  classes,  orders,  or  families,  now  widely  distinct, 
without  connecting  links  or  intermediate  forms.  For 
example  :  The  earliest  vertebrates  were  fishes,  but  not 
typical  fishes.  On  the  contrary,  they  were  fishes  so 
closely  connected  by  many  characters  with  amphibian 
reptiles,  that  we  hardly  know  whether  to  call  some  of 
them  reptilian  fishes,  or  fish-like  reptiles.  From  these, 
as  from  a  common  vertebrate  stem,  were  afterward  sepa- 
rated, by  slow  changes  from  generation  to  generation,  in 
two  directions,  the  typical  fishes  and  the  true  reptiles. 
So,  also,  to  take  another  example,  the  first  birds  were  far 
different  from  typical  birds  as  we  now  know  them.  Thej 
were^  on  contrary,  birds  so  reptilian  in  character,  that 
there  is  still  some  doubt  whether  bird-characters  or  rep- 
tilian characters  predominate  in  the  mixture,  and  there- 
fore whether  they  ought  to  be  called  reptilian  birds  or 
bird-like  reptiles.  From  this  common  stem,  the  more 
specialized  modern  reptiles  branched  off  in  one  direction 
and  typical  birds  in  another,  and  intermediate  forms  be- 
came extinct ;  until  noio,  the  two  classes  stand  widely 
apart,  without  apparent  genetic  connection.  This  sub- 
ject will  be  more  fully  treated  hereafter,  and  other  ex- 
amples given.  These  two  will  be  sufficient  now  to  make 
the  idea  clear. 


ITS  SCOPE   AND   DEFINITION.  13 

Such  early  forms  combining  the  characters  of  two  or 
more  groups,  now  widely  separated,  were  called  by  Agas- 
siz  connecting  types,  comhining  types,  synthetic  types, 
and  sometimes  proplietic  types  ;  by  Dana,  comprelien- 
sive  types  ;  and  by  Huxley,  generalized  types.  They  are 
most  usually  known  now  as  generalized  types,  and  their 
widely-separated  outcomes  specialized  types.  Thus,  in 
general,  we  may  say  that  the  widely-separated  groups  of 
the  present  day,  when  traced  back  in  geological  times, 
approach  one  another  more  and  more  until  they  finally 
unite  to  form  common  stems,  and  these  in  their  turn 
unite  to  form  a  common  trunk.  From  such  a  common 
trunk,  by  successive  branching  and  rebranching,  each 
branch  taking  a  different  direction,  and  all  growing  wider 
and  wider  apart  (differentiation),  have  been  gradually 
generated  all  the  diversified  forms  which  we  see  at  the 
present  day.  The  last  leafy  ramifications — flower-bear- 
ing and  fruit-bearing — of  this  tree  of  life,  are  the  fauna 
and  flora  of  the  present  epoch.  The  law  might  be  called 
a  law  of  ramification,  of  specialization  of  the  parts,  and 
diversification  of  the  whole. 

h.  Law  of  Progress  of  the  Whole.— Many  imagine 
that  progress  is  the  one  law  of  evolution  ;  in  fact,  that 
evolution  and  progress  are  coextensive  and  convertible 
terms.  They  imagine  that  in  evolution  the  movement 
must  be  upward  and  onward  in  all  parts  ;  that  degener- 
ation is  the  opposite  of  evolution.  This  is  far  from  the 
truth.  There  is,  doubtless,  in  evolution,  progress  to 
higher  and  higher  planes  ;  but  not  along  every  line,  nor 


14  WHAT  IS  EVOLUTION? 

in  every  part  ;  for  this  would  be  contrar\'  to  the  law  of 
differentiation.  It  is  only  progress  of  the  whole  organic 
kingdom  in  its  entirety.  We  can  best  make  this  clear 
by  an  illustration.  A  growing  tree  branches  and  again 
branches  m  all  directions,  some  branches  going  upward 
some  sidewise,  and  some  downward — anywhere,  every- 
wdiere,  for  light  and  air ;  but  the  whole  tree  grows  ever 
taller  in  its  higher  branches,  larger  in  the  circumference 
of  its  outstretching  arms,  and  more  diversified  in  struct- 
ure. Even  so  the  tree  of  life,  by  the  law  of  differentia- 
tion, branches  and  rebranches  continually  in  all  direc- 
tions— some  branches  going  upward  to  higher  planes 
(progress),  some  pushing  horizontally,  neither  rising 
nor  sinking,  but  only  going  farther  from  the  general- 
ized origin  (specialization)  ;  some  going  downward  (de- 
generation), anywhere,  everywhere,  for  an  unoccupied 
place  in  the  economy  of  j^ature,  but  the  whole  tree 
grows  ever  higher  in  its  highest  parts,  grander  in  its 
proportions,  and  more  complexly  diversified  in  its 
structure. 

It  may  be  well  to  pause  here  a  moment  to  show  how 
this  mistaken  identification  of  evolution  with  progress 
alone,  without  modification  by  the  more  fundamental 
laws  of  differentiation,  has  given  rise  to  misconceptions 
ill  the  popular  and  even  in  the  scientific  mind.  The  bi- 
ologist is  continually  met  with  the  question,  '^Do  you 
mean  to  say  that  any  one  of  the  invertebrates,  such,  for 
instance,  as  a  spider,  may  eventually,  in  the  course  of 
successive  generations,  become  a  vertebrate,  or  that  a  dog 


ITS   SCOPE   AND   DEFINITION.  15 

or  a  monkey  is  on  the  highway  to  become  a  man  ?  "  By 
no  means.  There  is  but  one  straight  and  narrow  way  to 
the  highest  in  evolution  as  in  all  else,  and  few  there  be 
that  have  found  it — in  fact,  probably  two  or  three  oYily 
at  every  stejp.  The  animals  mentioned  above  have  di- 
verged from  that  way.  In  their  ancestral  history,  they 
have  missed  the  golden  opportunity,  if  they  ever  had 
it.  It  is  easy  to  go  on  in  the  way  they  have  chosen, 
but  impossible  to  get  back  on  the  ascending  trunk- 
line.  To  compare  again  with  the  growing  tree,  only 
one  straight  trunk-line  leads  upward  to  the  terminal 
bud.  A  branch  once  separated  must  grow  its  own  way, 
if  it  grow  at  all. 

Of  the  same  nature  is  the  mistake  of  some  extreme 
evolutionists,  such  as  Dr.  Bastian  and  Professor  Haeckel, 
and  of  nearly  all  anti-evolutionists,  viz.,  that  of  imagin- 
ing that  the  truth  of  evolution  and  that  of  spontaneous 
generation  must  stand  or  fall  together.  On  the  con- 
trary, if  life  did  once  arise  spontaneously  from  any  lower 
forces,  physical  or  chemical,  by  natural  process,  the  con- 
ditions necessary  for  so  extraordinary  a  change  could 
hardly  ie  expected  to  occur  lut  once  in  the  history  of  the 
earth.  They  are,  therefore,  noiu,  not  only  unreproduci- 
ble,  but  unimaginable.  Such  golden  opportunities  do 
not  recur.  Evolution  goes  only  onward.  Therefore,  the 
impossibility  of  the  derivation  of  life  from  non-life  now, 
is  no  more  an  argument  against  such  a  derivation  oiice, 
than  is  the  hopelessness  of  a  worm  ever  becoming  a  ver- 
tebrate now,  an  argument  against  the  derivative  origin 


16  WHAT  IS  EVOLUTION? 

of  vertebrates.  Doubtless  if  life  were  now  extinguished 
from  the  face  of  the  earthy,  it  could  not  again  be  rekin- 
dled by  any  natural  process  known  to  us  ;  but  the  same  is 
probably  true  of  every  step  of  evolution.  If  any  class — 
for  example,  mammals — were  now  destroyed,  it  could  not 
be  re-formed  from  any  other  class  now  living.  It  would 
be  necessary  to  go  back  to  the  time  and  conditions  of  the 
separation  of  this  class  from  the  reptilian  stem.  There- 
fore, the  falseness  of  the  doctrine  of  abiogenesis,*  so  far 
from  being  any  argument  against  evolution,  is  exactly 
what  a  true  conception  of  evolution  and  knowledge  of  its 
laws  would  lead  us  to  expect. 

c.  Law  of  Cyclical  Movement. — The  movement  of  evo- 
lution has  ever  been  onward  and  upward,  it  is  true,  but 
not  at  uniform  rate  in  the  whole,  and  especially  in  the 
parts.  On  the  contrar}^,  it  has  jDlainly  moved  in  succes- 
sive cycles.  The  tide  of  evolution  rose  ever  higher  and 
higher,  without  ebb,  but  it  nevertheless  came  in  succes- 
sive waves,  each  higher  than  the  preceding  and  overborne 
by  the  succeeding.  These  successive  cycles  are  the  dy- 
nasties or  reigns  of  Agassiz,  and  ages  of  Dana  ;  the  reign 
of  mollusks,  the  reign  of  fishes,  of  reptiles,  of  mammals, 
and  finally  of  man.  During  the  early  Palaeozoic  times 
(Cambrian  and  Silurian)  there  were  na  vertebrates,  f 
But  never  in  the  history  of  the  earth  were  mollusks  of 
greater  size,  number,   and  variety  of  form   than   then. 

*  Genesis  without  previous  life — spontaneou's  generation, 
f  Fishes  were  first  introduced  in  the  later   Siliirian  ;    but   became 
dominant  in  the  Devonian. 


ITS   SCOPE  AND  DEFINITION.  17 

They  were  truly  the  rulers  of  these  early  seas.  In  the 
absence  of  competition  of  still  higher  animals,  they  had 
things  all  their  own  way,  and  therefore  grew  into  a  great 
monopoly  of  power.  In  the  later  Palaeozoic  (Devonian) 
fishes  were  introduced.  They  increased  rapidly  in  size, 
number,  and  yariety  ;  and  being  of  higher  organization 
they  quickly  usurped  the  empire  of  the  seas,  while  the 
mollusca  dwindled  in  size  and  importance,  and  sought 
safety  in  a  less  conspicuous  position.  In  the  Mesozoic 
times,  reptiles,  introduced  a  little  earlier,*  finding  con- 
genial conditions  and  an  unoccupied  place  above,  rapidly 
increased  in  number,  variety,  and  size,  until  sea  and  land 
seem  to  have  swarmed  with  them.  Never  before  or  since 
have  reptiles  existed  in  such  numbers,  in  such  variety 
of  form,  or  assumed  such  huge  proportions  ;  nor  have 
they  ever  since  been  so  highly  organized  as  then.  They 
quickly  became  rulers  in  every  realm  of  Nature — rulers  of 
the  sea,  swimming  reptiles  ;  rulers  of  the  land,  walking 
reptiles  ;  and  rulers  of  the  air,  flying  reptiles.  In  the  un- 
equal contest,  fishes  therefore  sought  safety  in  subordina- 
tion. Meanwhile  mammals  were  introduced  in  the  Meso- 
zoic, but  small  in  size,  low  in  type  (marsupials),  and  by 
no  means  able  to  contest  the  empire  with  the  great  rep- 
tiles. But  in  the  Cenozoic  (Tertiary)  the  conditions  ap- 
parently becoming  favorable  for  their  development,  they 
rapidly  increased  in  number,  size,  variety,  and  grade  of 
organization,  and  quickly  overpowered  the  great  reptiles, 

*  Amphibians  were  introduced  in  the  Carboniferous,  but  true  reptile 
not  until  the  Permian. 


18  WHAT  IS  EVOLUTION? 

which  ahiiost  immediately  sank  into  the  subordinate  po- 
sition in  which  wt  now  find  them,  and  thus  found  com- 
parative safety.  Finally,  in  the  Quaternary,  appeared 
man,  contending  doubtfully  for  a  while,  with  the  great 
mammals,  but  soon  (in  Psychozoic)  acquiring  mastery 
through  superior  intelligence.  The  huge  and  dangerous 
mammals  were  destroyed  and  are  still  being  destroyed  ; 
the  useful  animals  and  plants  were  preserved  and  made 
subservient  to  his  wants;  and  all  things  on  the  face  of 
the  earth  are  being  readjusted  to  the  requirements  of  his 
rule.  In  all  cases  it  will  be  observed  that  the  rulers  were 
such  because,  by  reason  of  strength,  organization,  and  in- 
telligence, they  were  fittest  to  rule.  There  is  alw^ays  room 
at  the  top.  To  illustrate  again  by  a  growing  tree :  This 
successive  culmination  of  higher  and  higher  classes  may 
be  comj^ared  to  the  flowering  and  fruiting  of  successively 
higher  and  higher  branches.  Each  up2:)ermost  branch, 
under  the  genial  heat  and  light  of  direct  sunshine,  re- 
ceived in  abundance  by  reason  of  position,  grew  rapidly, 
flowered,  and  fruited  ;  but  quickly  dwindled  when  over- 
shadowed by  still  higher  branches,  which,  in  their  turn, 
monopolized  for  a  time  the  precious  sunshine. 

But  observe,  furthermore  :  when  each  ruling  class  de- 
clined in  importance,  it  did  not  perish,  but  continued  in 
a  subordinate  position.  Thus,  the  whole  organic  king- 
dom became  not  only  higher  and  higher  in  its  highest 
forms,  but  also  more  and  more  complex  in  its  structure 
and  in  the  interaction  of  its  correlated  parts.  The  whole 
process  and  its  result  is  roughly  represented  in  the  ac- 


ITS   SCOPE  AND   DEFINITION. 


19 


Silurian 


Devon,  and  Curb.      Mesozoic. 

Fig.  1. 


Tert'y  and  Quat.         Present. 


companjing  diagram,  Fig.  1,  in  which  A  B  represents 
the  course  of  geological  time  and  the  curve,  the  rise, 
culmination,  and  decline  of  successive  dominant  classes. 

The  Above  Three   Laws  are  Laws  of  Evolutioi^^. 

These  three  laws  we  have  shown  are  distinctly  recog- 
nizable in  the  succession  of  organic  forms  in  the  geologi- 
cal history  of  the  earth.  They  are,  therefore,  tindoubt- 
edly  the  general  laivs  of  succession.  Are  they  also  laws 
of  evolution  ?  Are  they  also  discoverable  in  embryonic 
development,  the  t^'pe  of  evolution  ?  They  are,  as  we 
now  proceed  to  show  : 

Differentiation. — In  reproduction  the  new  individual 
appears  :  1.  As  a  germ-ccW — a  single  microscopic  living 
cell.  3.  Then,  by  growth  and  multiplication  of  cells,  it 
becomes  an  egg.  This  may  be  characterized  as  an  aggre- 
gate of  similar  cells,  and  therefore  is  not  yet  differen- 
tiated into  tissues  and  organs.  In  other  words,  iX  is  not 
yet  visibly  organized  ;  for  organization  may  be  defined  as 
the  possession  of  different  parts,  performing  different 
functions,  and  all  co-operating  for  one  givoii  end,  viz., 
the  life  and  well-being  of  the  organism.  8.  Then  com- 
mences the  really  characteristic  process  of  development, 


20  WHAT  IS  EVOLUTION? 

viz.,  differentiation  or  diversification.  The  cells  are  at 
first  all  alike  iu  form  and  function,  for  all  are  globular 
in  form,  and  each  performs  all  the  functions  necessary 
for  life.  From  this  common  point  now  commences  de- 
velopment in  differe7it  directions,  which  may  be  com- 
pared to  a  branching  and  rebranching,  with  more  and 
more  complex  results,  according  as  the  animal  is  higher 
in  the  scale  of  organization  and  advances  toward  a  state 
of  maturity.  First,  the  cell-aggregate  {<^gg)  separates  into 
three  distinct  layers  of  cells,  called  ecto-blast,  en  do-blast, 
and  meso-blast.  These  by  further  differentiation  form  the 
three  fundamental  groups  of  organs  and  functions,  viz., 
the  nervous  system,  the  nutritive  system,  and  the  Mood 
system :  the  first  presiding  over  the  exchange  of  force  or 
influence,  by  action  and  reaction  with  the  environment, 
and  between  the  different  parts  of  the  organism  ;  the  sec- 
ond presiding  over  the  exchange  of  matter  with  the  envi- 
ronment, by  absorption  and  elimination  ;  the  third  presid- 
ing over  exchanges  of  matter  between  different  parts  of 
the  organism.  The  first  system  of  functions  and  organs 
may  be  compared  to  a  S3'stem  of  telegraphy,  foreign  and 
domestic  ;  the  second  to  foreign  commerce  ;  the  third  to 
an  internal  carrying-trade.  Following  out  any  one  of 
these  groups  in  higher  animals,  say  the  nervous  system,  it 
quickly  differentiates  again  into  two  sub-S3^stems,  viz.,  cer- 
ebro-spinal  and  ganglionic,  each  having  its  own  distinctive 
functions,  which  we  can  not  stoj?  to  explain.  Then  the 
cerebro-spinal  again  differentiates  into  voluntary  and  re- 
flex systems.    All  of  these  have  meanwhile  separated  into 


ITS   SCOPE   AND  DEFINITION.  21 

sensory  and  motor  centers  and  fibers.  Then,  taking  only 
the  sensory  fibers,  these  again  are  differentiated  into  five 
special  senses,  each  having  a  wholly  difi;erent  function. 
Then,  finally,  taking  any  one  of  these,  say  the  seiise  of 
touch  or  feeling,  this  again  is  differentiated  into  many 
kinds  of  fibers,  each  responding  to  a  different  impression, 
some  to  heat,  others  to  cold,  still  others  to  pressure,  etc. 
We  have  taken  the  nervous  svstem  :  but  the  same  differ- 
entiation  and  redifferentiation  takes  place  in  all  other 
systems,  and  is  carried  to  higher  and  higher  points  ac- 
cording to  the  position  in  the  scale  of  the  animal  which 
is  to  be  formed. 

Or,  to  vary  the  mode  of  presentation  a  little,  the  cells 
of  the  original  aggregate,  commencing  all  alike,  imme- 
diately begin  to  take  on  different  forms,  in  order  to  per- 
form different  functions.  Some  cells  take  on  a  certain 
form  and  aggregate  themselves  to  form  a  peculiar  tissue 
which  we  call  muscle,  and  which  does  nothing  else,  can 
do  nothing  else,  than  contract  under  stimulus.  Another 
group  of  cells  take  on  another  peculiar  form  and  aggre- 
gate themselves  to  form  another  and  very  different  tis- 
sue, viz.,  nervous  tissue,  which  does  nothing  and  can  do 
nothing  but  carry  influence  back  and  forth  between  the 
great  external  world  and  the  little  world  of  consciousness 
within.  Still  another  group  of  cells  take  still  another 
forai  and  aggregate  to  form  still  another  tissue,  viz.,  the 
ep^tlielial,  whose  only  function  is  to  absorb  nutritive  and 
eliminate  waste  matters.  Thus,  by  differentiation  of 
form  and  limitation  of  function,  or  division  of  labor,  the 


22  WHAT  IS  EVOLUTION? 

different  parts  of  the  organism  are  bound  more  and  more 
closely  together  by  mutnal  dependence,  and  the  whole 
becomes  more  and  more  distinctly  individuated,  and 
separation  of  parts  becomes  more  and  more  a  mutilation, 
and  finally  becomes  impossible  without  death.  This  pro- 
cess, as  already  said,  reaches  its  highest  point  only  in  the 
later  stages  of  deyelopment  of  the  highest  animals. 

Progress. — The  law  of  progress  is,  of  course,  admitted 
to  be  a  law  of  ontogeny  ;  but  observe  here,  also,  it  is  true 
only  of  the  whole  and  not  necessarily  of  all  the  j^arts,  ex- 
cept from  the  point  of  view  of  the  ichole.  Thus,  for  ex- 
ample, starting  all  from  a  comnmn  form  or  generalized 
type,  some  cells  advance  to  the  dignity  of  brain-cells, 
whose  function  is  somehow  connected  with  the  genera- 
tion or  at  least  the  manifestation  of  thought,  will,  and 
emotion  ;  other  cells  descend  to  the  position  of  kidney- 
cells,  whose  sole  function  is  the  excretion  of  urine.  But 
here,  also,  the  highest  cells  are  successively  higher,  and 
the  whole  aggregate  is  successively  nobler  and  more  com- 
plex. It  is  again  a  branching  and  rebranching,  in  ev- 
ery direction,  some  going  upward,  some  downward,  some 
horizontally,  anywhere,  everywhere,  to  increase  the  com- 
plexity of  relations  internal  and  external,  and  therefore 
to  elevate  the  plane  of  the  whole. 

Cyclical  Movement.— Lastly,  the  law  of  cyclical  move- 
ment is  also  a  law  of  ontogeny  and  therefore  of  evolution. 
This  law,  however,  is  less  fundamental  than  the  other 
two,  and  is,  therefore,  less  conspicuous  in  the  ontogenic 
than  in  the  i>hylogenic  series.     It  is  conspicuou'S  only  in 


ITS   SCOPE   AND  DEFINITION".  23 

the  later  stages  of  ontogeny,  and  in  other  higher  kinds 
of  evolution,  such  as  social  evolution.  For  example,  in 
the  ontogenic  development  of  the  body  and  mind  from 
childhood  to  manhood  we  have  plainly  successive  culmi- 
nations and  declines  of  higher  and  higher  functions.  In 
bodily  development  we  have  culminating  first  the  nutri- 
tive functions,  then  the  reproductive  and  muscular,  and 
last  the  ceredral.  In  mental  development  we  have  cul- 
mination first  of  the  receptive  and  retentive  faculties  in 
childhood,  then  of  imaginative  and  aesthetic  faculties  in 
youth  and  young  manhood  ;  then  of  the  reflective  and 
elaborative  faculties — the  faculties  of  productive  work  in 
mature  manhood  ;  and,  finally,  the  moral  and  religious 
sentiments  in  old  age.  The  first  gathers  and  stores  ma- 
terials ;  the  second  vivifies  and  makes  them  plastic 
building  materials  ;  the  third  uses  them  in  actual  con- 
structive work — in  building  the  temple  of  science  and 
philosophy ;  and  the  fourth  dedicates  that  temple  only 
to  noblest  purposes. 

Observe  here,  also,  that  when  each  group  of  faculties 
culminates  and  declines,  it  does  not  perish,  but  only  be- 
comes subordinate  to  the  next  higher  dominant  group, 
and  the  whole  psychical  organism  becomes  not  only 
higher  and  higher  in  its  highest  j^arts,  but  also  more  and 
more  complex  in  its  structure  and  in  the  interaction  of 
its  correlated  parts. 

Observe,  again,  the  necessity  laid  upon  us  by  this  law — 
the  necessity  of  continued  evolution  to  the  end.  Child- 
hood,  beautiful   childhood,   can   not   remain  —  it   must 


24  WHAT  IS  EVOLUTIO^^? 

quickly  pass.  If,  with  the  decline  of  its  characteristic 
faculties,  the  next  higher  group  characteristic  of  youth 
do  not  increase  and  become  dominant,  then  the  glory  of 
life  is  already  past  and  deterioration  begins.  Have  we 
not  all  seen  sad  examples  of  this  ?  Youth,  glorious 
youth,  must  also  pass.  If  the  next  higher  group  of  re- 
flective and  elaborative  faculties  do  not  arise  and  domi- 
nate, then  progressive  deterioration  of  character  com- 
mences here — thenceforward  the  whole  nature  becomes 
coarse,  as  we  so  often  see  in  young  men,  or  else  shrivels 
and  withers,  as  we  so  often  see  in  young  women,  final- 
ly, manhood,  strong  and  self-relying  manhood,  must  also 
pass.  If  the  moral  and  religious  sentiments  have  not 
been  slowly  growing  and  gathering  strength  all. along, 
and  do  not  now  assert  their  dominance  over  the  whole 
man,  then  commences  the  final  and  saddest  decline  of 
all,  and  old  age  becomes  the  pitiable  thing  we  so  often 
see  it.  But,  if  the  evolution  have  been  normal  through- 
out ;  if  the  highest  moral  and  religious  nature  have  been 
gathering  strength  through  all,  and  now  dominates  all, 
then  the  psychic  evolution  rises  to  the  end — then  the 
course  of  life  is  like  a  wave  rising  and  cresting  only  at 
the  moment  of  its  dissolution,  or,  like  the  course  of  the 
sun,  if  not  brightest  at  least  most  glorious  in  its  setting. 
And  thus — may  we  not  hope  ?— the  glories  of  the  close  of 
a  well-spent  life  become  the  pledge  and  harbinger  of  an 
eternal  to-morrow  ? 

We  have  thus  far  illustrated  the  three  laws  of  succes- 
sion of  organic  forms  by  ontogen}',  because  this  is  the 


ITS  SCOPE   AND  DEFINITION.  25 

type  of  eyolution  ;  but  they  may  be  illustrated  also  bv 
other  forms  of  evolution.  Next  to  the  development  of 
the  individual,  undoubtedly  the  progress  of  society  fur- 
nishes the  best  illustration  of  these  laws. 

Commencing  with  a  condition  in  which  each  indi- 
vidual performs  all  necessary  social  functions,  but  very 
imperfectly ;  in  which  each  individual  is  his  own  shoe- 
maker and  tailor,  and  house-builder  and  farmer,  and 
therefore  all  persons  are  socially  alike ;  as  society  ad- 
vances, the  constituent  members  begin  to  diverge,  some 
taking  on  one  social  function  and  some  another,  until  in 
the  highest  stages  of  social  organization  this  diversifica- 
tion or  division  and  subdivision  of  labor  reaches  its  high- 
est point,  and  each  member  of  the  aggregate  can  do  per- 
fectly but  one  thing.  Thus,  the  social  organism  becomes 
more  and  more  strongly  bound  together  by  mutual  de- 
pendence, and  separation  becomes  mutilation.  I  do  not 
mean  to  say  that  this  extreme  is  desirable,  but  only  that 
an  approach  to  this  is  a  natural  law  of  social  develop- 
ment.    Is  not  this  the  laiu  of  differentiation? 

So  also  progress  is  here,  as  in  other  forms  of  evo- 
lution— a  progress  of  the  ivhole,  but  not  necessarily  of 
every  part.  Some  members  of  the  social  aggregate  ad- 
vance upiuard  to  the  dignity  of  statesmen,  philosophers, 
and  poets ;  some  advance  doivnward  to  the  position  of 
scavengers  and  sewer-cleansers."^  But  the  highest  mem- 
bers are  progressively  higher,  and  the  whole  aggregate  is 

*  Of  coui^  I  mean  downward  in  social  function.     Individually  the 
scavenger  may  be  nobler  than  the  statesman. 


26  WHAT  IS  EVOLUTION? 

progressively  grander  and  more  complex  in  structure  and 
functions. 

So,  again,  the  laiu  of  cyclical  movement  is  equally 
conspicuous  here.  Society  everywhere  advances,  not  uni- 
formly, but  by  successive  waves,  each  higher  than  the 
last ;  each  urged  by  a  new  and  higher  social  force, 
and  embodying  a  new  and  higher  phase  of  civilization. 
Again  :  as  each  phase  declines,  its  characteristic  social 
force  is  not  lost,  but  becomes  incorporated  into  the  next 
higher  phase  as  a  subordinate  j)i'iiiciple,  and  thus  the 
social  organism  as  a  whole  becomes  not  only  higher  and 
higher,  but  also  more  and  more  complex  in  the  mutual 
relations  of  its  interacting  social  forces. 

Let  us  not  be  misunderstood,  however.  There  is  un- 
doubtedly in  social  evolution  something  more  and  higher 
than  we  have  described,  but  which  does  not  concern  us 
here,  except  to  guard  against  misconstruction.  There 
is  in  society  a  voluntary  progress  wholly  different  from 
the  evolution  we  have  been  describing.  In  true  or  ma- 
terial evolution  natural  law  works  for  the  betterment  of 
the  whole  utterly  regardless  of  the  elevation  of  the  indi- 
vidual, and  the  individual  contributes  to  the  advance  of 
the  whole  quite  unconsciously  while  striving  only  for  his 
own  betterment.  This  unconscious  evolution  by  natural 
law  inherited  from  the  animal  kingdom  is  conspicuous 
enough  in  society,  especially  in  its  early  stages,  but  we 
would  make  a  great  mistake  if  we  imagined,  as  some  do, 
that  this  is  all.  Besides  the  unconscious  evolution  by 
natural  laws,  inlierited  from  below,  there  is  a  higher  evo- 


ITS   SCOPE   A^-D  DEFINITION".  2T 

lution,  inherited  from  above,  indissolubl}^  connected  with 
man's  spiritual  nature — a  conscious,  yoluntary  strivino- 
of  the  best  members  of  the  social  aggregate  for  the  bet- 
terment of  the  whole — a  conscious,  Toluntary  striving 
both  of  the  individual  and  of  society  toward  a  recog- 
nized ideal.  In  the  one  kind  of  evolution  the  fittest 
are  those  most  in  harmony  with  the  environment,  and 
which  therefore  always  survive  ;  in  the  other,  the  fittest 
are  those  most  in  harmony  with  the  ideal,  and  which 
often  do  not  survive.  The  laws  of  this  free  voluntary 
progress  are  little  understood.  They  are  of  supreme 
importance,  but  do  not  specially  concern  us  here.  We 
will  speak  of  it  again  in  another  chapter. 

The  three  laws  above  mentioned  might  be  illustrated 
equally  well  by  all  other  forms  of  evolution.  We  have 
selected  only  those  which  are  most  familiar.  They  may, 
therefore,  be  truly  called  the  laws  of  evolution.  We 
have  shown  that  they  are  the  laws  of  succession  of  or- 
ganic forms. 

III.  Change  by  Means  of  Resident  Forces.— Thus  far 
in  our  argument  I  suppose  that  most  well-informed  men 
will  raise  no  objection.  It  will  be  admitted,  I  think, 
even  by  those  most  bitterly  opposed  to  the  theory  of  evo- 
lution, that  there  has  been  throughout  the  whole  geologi- 
cal history  of  the  earth  an  onward  movement  of  the  or- 
ganic kingdom  to  higher  and  higher  levels.  It  will  be 
admitted,  also,  that  there  is  a  grand  and  most  significant 
resemblance  between  the  course  of  development  of  the 
organic  kingdom  and  the  course  of  embryonic  develop- 


28  WHAT  IS  EYOLUTION^? 

ment — between  the  laws  of  succession  of  organic  forms 
and  the  laws  of  ontogenic  evolution.  But  there  is  an- 
other essential  element  in  ontogenic  evolution.  It  is 
that  the  forces  or  causes  of  evolution  are  natural ;  that 
they  reside  in  the  thing  developing  and  in  the  reacting 
environment.  This  we  know  is  true  of  embryonic  devel- 
opment ;  is  it  true  also  of  the  geologic  succession  of  or- 
ganic forms  ?  It  IS  true  of  ontogeny ;  is  it  true  also  of 
phylogeny  ?  If  not,  then  only  by  a  metaphor  can  we  call 
the  process  of  change  in  the  organic  kingdom  throughout 
geological  history  an  evolution.  This  is  the  point  of 
discussion,  and  not  only  of  discussion,  but,  alas  !  of 
heated  and  even  angry  dispute.  The  field  of  discussion 
is  thus  narrowed  to  this  third  point  only. 

Before  stating  the  two  opposite  views  of  the  cause  of 
evolution,  it  is  necessary  to  remind  tlie  reader  that  when 
the  evolutionist  speaks  of  the  forces  that  determine  pro- 
gressive changes  in  organic  forms  as  resident  or  inherent, 
all  that  he  means,  or  ought  to  mean,  is  that  they  are 
resident  in  the  same  sense  as  all  natural  forces  are  resi- 
dent ;  in  the  same  sense  that  the  vital  forces  of  the  em- 
bryo are  resident  in  the  embryo,  or  that  the  forces  of  the 
development  of  the  solar  system  according  to  the  nebular 
or  any  other  cosmogonic  hypotheses  are  resident  in  that 
system.  In  other  words,  they  mean  only  that  they  are 
natural,  not  supernatural.  This  does  not,  of  course, 
touch  that  deeper,  that  deepest  of  all  questions,  viz., 
the  essential  nature  and  origin  of  natural  forces  ;  how 
far  they  are  independent  and  self-existent,  and  how  far 


ITS   SCOPE  AND  DEFINITION.  29 

they  are  only  modes  of  divine  energy.  This  is  a  question 
of  philosophy,  not  of  science.  This  question  is  briefly 
discussed  in  another  place  (Part  III,  Chap.  Ill)  ;  it  does 
not  immediately  concern  us  here. 

The  Two  Views  briefly  Contrasted.— As  already  stated, 
all  will  admit  a  grand  resemblance  between  the  stages  of 
embryonic  development  and  those  of  the  development  of 
the  organic  kingdom.  This  was  first  brought  out  clearly 
by  Louis  Agassiz,  and  is,  in  fact,  the  greatest  result  of 
his  life-work.  All  admit,  also,  that  the  embryonic  de- 
velopment is  a  natural  process.  Is  the  development  of 
the  organic  kingdom  also  a  natural  process  ?  All  biolo- 
gists of  the  present  day  contend  that  it  is  ;  all  the  old- 
school  naturalists,  with  Agassiz  at  their  head,  and  all 
anti-evolutionists  of  every  school,  contend  that  it  is  not. 
We  take  Agassiz  as  the  type  of  this  school,  because  he 
has  most  fully  elaborated  and  most  distinctly  formulated 
this  view.  As  formulated  by  him,  it  has  stood  in  the 
minds  of  many  as  an  alternative  and  substitute  for  evo- 
lution. 

According  to  the  evolutionists,  all  organic  forms, 
"whether  species,  genera,  families,  orders,  classes,  etc.,  are 
variable,  and,  if  external  conditions  favor,  these  varia- 
tions accumulate  in  one  direction  and  gradually  produce 
new  forms,  the  intermediate  links  being  usually  destroyed 
or  dying  out.  According  to  Agassiz,  the  higher  groups, 
such  as  genera,  families,  orders,  etc.,  are  indeed  vari- 
able by  the  introduction  of  new  species,  but  sjDecics  are 
the  ultimate  elements  of  classification,  and,  like  the  ul- 


30  WHAT  IS  EVOLUTION"? 

timate  elements  of  chemistry,  are  unchangeable  ;  and, 
therefore,  the  speculations  of  the  evolutionist  concerning 
the  transmutation  of  species  are  as  vain  as  were  the  spec- 
ulations of  the  alchemists  concerning  the  transmutation 
of  metals — that  the  origin  of  man,  for  example,  from 
any  lower  sj^ecies  is  as  impossible  as  the  origin  of  gold 
from  any  baser  metal.  Both  sides  admit  frequent  change 
of  species  during  geological  history,  but  one  regards  the 
change  as  a  change  by  gradual  transmutation  of  one 
species  into  another  through  successive  generations  and 
by  natural  process,  the  other  as  change  by  substitution 
of  one  species /or  another  by  direct  supernatural  creative 
act.  Both  admit  the  gradual  development  of  the  organic 
kingdom  as  a  whole  through  stages  similar  to  those  of 
embryonic  development ;  but  the  one  regards  the  whole 
process  as  natural,  and  therefore  strictly  comparable  to 
embryonic  development,  the  other  as  requiring  frequent 
special  interference  of  creative  energy,  and  therefore 
comparable  rather  to  the  development  of  a  building  un- 
der the  hand  and  according  to  the  preconceived  plan  of 
an  architect — a  plan,  in  this  case,  conceived  in  eternity 
and  carried  out  consistently  through  infinite  time.  It  is 
seen  that  the  essential  point  of  difference  is  this  :  The 
one  asserts  the  variability  of  species  (if  conditions  favor, 
and  time  enough  is  given)  without  limit ;  the  other  as- 
serts the  permanency  of  specific  forms,  or  their  variabil- 
ity only  within  narrow  limits.  The  one  asserts  the  origin 
of  species  by  ^'descent  with  modificatiG7is'''j  the  other, 
the  origin  of  species  by  '^special  act  of  creation.^^     The 


\/' 


ITS  SCOPE  AND  DEFINITION.  31 

one  asserts  the  law  of  continuity  (i.  e.,  that  each  stage  is 
the  natural  outcome  of  the  immediately  preceding  stage) 
in  this,  as  in  every  other  department  of  Nature ;  the 
other  asserts  that  the  law  of  continuity  (i.  e.,  of  cause 
and  effect)  does  not  hold  in  this  department ;  that  the 
links  of  the  chain  of  changes  are  discontinuous,  the  con- 
nection between  them  being  intellectual,  not  physical. 

So  much  for  sharp  contrasting  characterization  of  the 
two  "views,  necessary  for  clear  understandmg  of  much 
that  follows.  We  y/ill  have  to  give  them  more  fully 
hereafter  when  we  take  up  the  evidences  of  evolution  in 
Part  II. 


3 


CHAPTER  11. 

THE    BELATIOI^"    OF    LOUIS    AGASSIZ    TO    THE    THEOEY    OF 

EVOLUTIOI^. 

In"  order  to  clear  up  the  conception  of  evolution,  it  is 
necessary  to  give  a  brief  history  of  the  idea,  and  espe- 
cially to  explain  the  relation  of  Louis  Agassiz  to  that 
theory.  This  is  the  more  necessary,  because  there  is  a 
deep  and  wide-spread  misunderstanding  on  this  subject, 
and  thus  scant  justice  has  been  done  our  great  naturalist, 
especially  by  the  English  and  Germans  ;  and  also  because 
this  relation  is  an  admirable  illustration  of  an  important 
principle  m  scientific  philoso23hy. 

Like  all  great  ideas,  we  find  the  first  germs  of  this  in 
Greek  philosophy,  in  the  cosmic  speculations  of  Thales 
and  Pythagoras,  l^ext  (about  100  b.  c.)  we  find  it  more 
clearly  expressed  by  the  Eoman  thinker,  Lucretius,  in 
his  great  philosophic  poem  entitled  "De  Eerum  Natura." 
After  a  dormancy  of  nearly  eighteen  centuries  it  next 
emerges  with  still  more  clearness  in  the  theological  specu- 
lations of  Swedenborg  and  the  philosophical  speculations 
of  Kant.  All  these  we  pass  over  with  bare  mention,  be- 
cause these  thinkers  approached  the   subject  from   the 


RELATION   OF   AGASSIZ  TO  EVOLUTION.         33 

philosophic  rather  than  the  scientific  side — in  the  meta- 
physical rather  than  the  scientific  spirit. 

The  first  serious  attempt  at  scientific  presentation  of 
the  subject  was  by  the  celebrated  naturalist,  Lamarck,  in 
a  work  entitled  **  Philosophic  Zoologique,"  published  in 
1809.  It  is  not  necessary,  in  this  rapid  sketch,  to  give  a 
full  account  of  Lamarck's  views.  Suffice  it  to  say  that 
the  essential  idea  of  evolution,  viz.,  the  indefinite  vari- 
ability and  the  derivative  origin  of  species,  was  insisted 
on  with  great  learning  and  skill,  and  illustrated  by  many 
examples.  With  Lamarck,  the  factors  of  evolution  or 
causes  of  change  of  organic  forms  were — 1.  Modification 
of  organs  in  function  and  therefore  in  structure,  by  a 
changing  environment — external  factor  ;  and,  2.  Modifi- 
cation of  organs  by  use  and  disuse — internal  factor.  In 
both  cases  the  modifications  are  inherited  and  increased 
from  generation  to  generation,  without  limit.  This  sec- 
ond factor  seems  to  have  taken,  in  the  mind  of  Lamarck, 
the  somewhat  vague  and  transcendental  form  of  aspira- 
tion or  upward  striving  of  the  animal  toward  higher 
conditions.  These  are  acknowledged  to-day  as  true  fac- 
tors of  evolution,  but  the  distinctively  Darwinian  factor, 
viz.,  '^divergent  variation  and  natural  selection,"  was 
not  then  thought  of.  The  publication  of  Lamarck's 
views  produced  a  powerful  impression,  but  only  for 
a  little  while.  Pierced  by  the  shafts  of  ridicule  shot 
by  nimble  wits  of  Paris,  and  crushed  beneath  the 
heavy  weight  of  the  authority  of  Cuvier,  the  greatest 
naturalist  and  comparative  anatomist  of  that  or  perhaps 


34  WHAT  IS  EVOLUTION? 

of  any  time,  it  fell  almost  still-born.  I  believe  it  was 
best  that  it  should  thus  perish.  Its  birth  was  prema- 
ture ;  it  was  not  fit  to  live.  The  world  was  not  yet  pre- 
pared for  a  true  scientific  theory.  Nevertheless,  the 
work  was  not  without  its  effect  upon  some  of  the  most 
advanced  thinkers  of  that  time  ;  upon  Saint-Hilaire  and 
Comte  in  France,  and  upon  Goethe  and  Oken  in  Ger- 
many. It  was  good  seed  sown  and  destined  to  spring  up 
and  bear  fruit  in  suitable  environment ;  but  not  yet. 

The  next  attempt  worthy  of  attention  in  this  rapid 
sketch  is  that  of  Robert  Chambers,  in  a  little  volume  en- 
titled '^Vestiges  of  a  Natural  History  of  Creation,"  pub- 
lished in  1844.  It  was  essentially  a  reproduction  of 
Lamarck's  views  in  a  more  popular  form.  It  was  not  a 
truly  scientific  work  nor  written  by  a  scientific  man.  It 
was  rather  an  appeal  from  the  too  technical  court  of  sci- 
ence to  the  supposed  wider  and  more  unprejudiced  court 
of  popular  intelligence.  It  was  therefore  far  more  elo- 
quent than  accurate ;  far  more  specious  than  profound. 
It  w^as,  indeed,  full  of  false  facts  and  inconsequent  rea- 
sonings. Nevertheless,  it  produced  a  very  strong  impres- 
sion on  the  thinking,  popular  mind.  But  it  also  quickly 
fell,  pierced  by  keen  shafts  of  ridicule,  and  crushed  be- 
neath the  heavy  weight  of  the  authority  of  all  the  most 
prominent  naturalists  of  that  time,  with  Agassiz  at  their 
head.  The  question  for  the  time  seemed  closed.  I  be- 
lieve, again,  it  was  best  so,  for  the  time  was  not  yet  fully 
ripe. 

I  know  full  well  that  many  think  with  Haeckel  that 


RELATION  OF   AGASSIZ   TO  EVOLUTION.         35 

biology  was  kept  back  half  a  century  by  the  baneful  au- 
thority of  Cuyier  and  Agassiz  ;  but  I  can  not  think  so. 
The  hypothesis  was  contrary  to  the  facts  of  science  as 
then  knoivn  and  understood.  It  was  conceiyed  in  the 
spirit  of  baseless  siDcculation,  rather  than  of  cautious 
induction  ;  of  skillful  elaboration  rather  than  of  earnest 
truth-seeking.  Its  general  acceptance  would  have  de- 
bauched the  true  spirit  of  science.  I  repeat  it  :  the  time 
was  not  yet  ripe  for  a  scientific  theory.  The  ground 
must  first  be  cleared  and  a  solid  foundation  built ;  an  in- 
superable  ohstacle  to  hearty  rational  acceptance  must 
first  be  removed,  and  an  inductive  lasis  must  be  laid. 

The  Obstacle  removed. — The  obstacle  in  the  way  of 
the  acceptance  of  the  derivative  origin  of  species  was  the 
then  prevalent  7iotion  concerning  the  nature  of  life.  We 
must  briefly  sketch  the  change  which  has  taken  place  in 
the  last  forty  years  in  our  ideas  on  this  subject. 

Until  about  forty  years  ago,  the  different  forces  of 
Nature,  such  as  gravity,  electricity,  magnetism,  light, 
heat,  chemical  affinity,  etc.,  were  supposed  to  be  entirely 
distinct.  The  realm  of  Nature  was  divided  up  into  a 
number  of  distinct  and  independent  principalities,  each 
subject  to  its  own  sovereign  force  and  ruled  by  its  own 
petty  laws.  About  that  time  it  began  to  be  evident,  and 
is  now  universally  acknowledged,  that  all  these  forces  are 
but  different /on7Z5  of  one,  universal,  omnipresent  energy, 
and  are  transmutable  unto  one  another  back  and  forth 
without  loss.  This -is  the  doctrine  of  correlation  of 
forces  and  conservation  of  energy,  one  of  the  grandest 


36  WHAT   IS  EVOLUTION? 

ideas  of  modern  times.  But  one  force  seemed  still  to  be 
an  exception.  Life-force  was  still  believed  to  be  a  pe- 
culiar, mysterious  principle  or  entity,  standing  above 
other  forces  and  subordinating  them ;  not  correlated 
with,  not  transmutable  unto,  nor  derivable  from,  other 
and  lower  forces,  and  therefore  in  some  sense  super- 
natural. Now,  if  this  be  true  of  li^mg  forces,  it  is  per- 
fectly natural,  yea,  almost  necessary,  to  believe  that  liv- 
ing/orms  are  wholly  different  from  other  forms  in  their 
origin.  New  forms  of  dead  matter  may  be  derived,  but 
new  living  forms  are  underived.  Other  new  forms  come 
by  natural  process,  new  organic  forms  by  supernatural 
process.  The  conclusion  was  almost  unavoidable.  But 
soon  vital  force  also  yielded  to  the  general  law  of  correla- 
tion of  natural  forces.  Vital  forces  are  also  transmutable 
into  and  derivable  from  physical  and  chemical  forces. 
Sun-force,  falling  on  the  green  leaves  of  plants,  is  ab- 
sorbed and  converted  into  vital  force,  disappears  as  light 
to  reappear  as  life.  The  amount  of  life-force  generated 
is  measured  by  the  amount  of  light  extinguished.  The 
same  is  true  of  animal  life.  As  in  the  steam-engine  the 
locomotive  energy  is  derived  from  the  fuel  consumed  and 
measured  by  its  amount,  so  in  the  animal  body,  the  ani- 
mal heat  and  animal  force  are  derived  from  and  measured 
by  the  food  and  tissue  consumed  by  combustion.  Thus, 
vital  force  may  be  regarded  as  so  much  force  withdrawn 
from  the  general  fund  of  chemical  and  physical  forces,  to 
be  again  refunded  without  loss  at  death.  This  obstacle 
is,  therefore,  now  removed.     If  vital  force  falls  in  the 


RELATION"   OF  AGASSIZ   TO  EVOLUTION.         37 

same  category  as  other  natural  forces,  there  is  no  reason 
why  living  forms  should  not  fall  into  the  same  category 
in  this  regard  as  other  natural  forms.  If  new  forms  of 
dead  matter  are  derived  from  old  forms  by  modification, 
according  to  physical  laws,  there  is  no  reason  why  new 
living  forms  should  not  also  be  derived  from  old  forms 
by  modification  according  io  pliy biological  laws.  Thus, 
at  last,  the  obstacle  was  removed — the  ground  was 
cleared. 

The  Basis  laid. — But  Science  is  not  content  with  re- 
moval of  a  priori  objections.  She  must  also  have  posi- 
tive proofs.  The  ground  must  not  only  be  cleared,  but  a 
true  inductive  basis  of  facts,  and  especially  of  laws  and 
methods,  must  be  laid.  This  was  the  life-wovh  of  Agas- 
siz.  Yes,  as  strange  as  it  may  seem  to  some,  it  is  never- 
theless true  that  the  whole  inductive  basis,  uj^on  which 
was  afterward  built  the  modern  theory  of  evolution,  was 
laid  by  Agassiz,  although  he  himself  persistently  refused 
to  build  upon  it  any  really  scientific  superstructure.  It 
is  plain,  then,  that  all  attempts  at  building  previous  to 
Agassiz's  work  must,  of  necessity,  have  resulted  in  an 
unsubstantial  structure — an  edifice  built  on  sand,  which 
could  not  and  ought  not  to  stand.  I  must  stop  here  in 
order  to  explain  somewhat  fully  this  important  point, 
and  thus  to  give  due  credit  to  the  work  of  Agassiz. 

The  title  of  any  scientist  to  greatness  must  be  deter- 
mined, not  so  much  by  the  multitude  of  new  facts  he  has 
discovered  as  by  the  new  laws  he  has  established,  and 
especially  by  the  new  methods  he  has  inaugurated  or  per- 


38  WHAT  IS  EVOLUTION? 

fected,  Now,  I  tliink  it  can  be  shown  that  to  Agassiz^, 
more  than  to  any  other  man,  is  due  the  credit  of  having 
established  the  laws  of  succession  of  living  forms  in  the 
geological  history  of  the  earth — laws  upon  which  must 
rest  any  true  theory  of  evolution.  Also,  that  to  him, 
more  than  to  any  other  man,  is  due  the  credit  of  having 
perfected  the  method  (method  of  comparison)  by  the  use 
of  which  alone  biological  science  has  advanced  so  rapidly 
in  modern  times.  This  is  high  praise.  I  wish  to  justify 
it.     I  begin  with  the  method. 

Scientific  methods  bear  the  same  relation  to  intellect- 
ual progress  that  tools,  instruments,  machines,  mechani- 
cal contrivances  of  all  sorts,  bear  to  material  progress. 
They  are  intellectual  contrivances — indirect  ways  of  ac- 
complishing results  far  too  hard  for  bare-handed,  unaided 
intellectual  strength.  As  the  civilized  man  has  little  or 
no  advantage  over  the  savage  in  bare-handed  strength  of 
muscle,  and  the  enormous  superiority  of  the  latter  in 
accomplishing  material  results  is  due  wholly  to  the  use 
of  mechanical  contrivances  or  machines  ;  even  so,  in  the 
higher  sphere  of  intellect,  the  scientist  makes  no  preten- 
sion to  the  possession  of  greater  unaided  intellectual 
strength  than  belongs  to  the  uncultured  man,  or  even 
perhaps  to  the  savage.  The  amazing  intellectual  results 
achieved  by  science  are  due  wholly  to  the  use  of  intellect- 
ual contrivances  or  scientific  methods.  As  in  the  lower 
sphere  of  material  progress  the  greatest  benefactors  of 
the  race  are  the  inventors  or  perfecters  of  new  mechani- 
cal contrivances  or  machines,  so  also  in  the  higher  sphere 


RELATION   OF  AGASSIZ   TO   EVOLUTION.         39 

of  intellectual  progress  the  greatest  benefactors  of  the 
race  are  the  inventors  or  perfecters  of  new  intellectual 
contrivances  or  methods  of  researcJi. 

To  illustrate  the  power  of  methods,  and  the  necessity 
of  their  use,  take  the  case  of  the  method  of  notation,  so 
characteristic  of  mathematics,  and  take  it  even  in  its 
simplest  and  most  familiar  form  :  Nine  numeral  figures, 
having  each  a  value  of  its  own,  and  another  dependent 
upon  its  position ;  a  few  letters,  a  and  h,  and  x  and  y, 
connected  by  symbols,  -J-  and  —  and  =  :  that  is  all.  And 
yet,  by  the  use  of  this  simple  contrivance,  the  dullest 
school-boy  accomplishes  intellectual  results  which  would 
defy  the  utmost  efforts  of  the  unaided  strength  of  the 
greatest  genius.  And  this  is  only  the  simplest  tool-form 
of  this  method.  Think  of  the  results  accomplished  by 
the  use  of  the  more  complex  machinery  of  the  higher 
mathematics  ! 

Take  next  the  method  of  experiment  so  characteristic 
of  physics  and  chemistry.  The  phenomena  of  the  external 
world  are  far  too  complex  and  far  too  much  affected  by 
disturbing  forces  and  modifying  conditions  to  be  under- 
stood at  once  by  bare,  unaided  intellectual  insight.  They 
must  first  be  simplified.  The  physicist,  therefore,  con- 
trives artificial  phenomena  under  ideal  conditions.  He 
removes  one  complicating  condition  after  another,  one 
disturbing  cause  and  then  another,  watching  meanwhile 
the  result,  until  finally  the  necessary  condition  and  the 
true  cause  are  discovered.  On  this  method  rests  the 
whole  fabric  of  the  ph3"sical  and  chemical  sciences. 


40  WHAT   IS   EVOLUTION"? 

But  when  we  rise  still  higher,  viz.j.  into  the  plane  of 
life,  the  phenomena  of  Nature  become  still  more  com- 
plex and  difficult  to  understand  directly ;  and  yet  just 
here,  where  we  are  the  most  powerless  without  some 
method,  our  method  of  experiment  almost  wholly  fails 
us.  The  phenomena  of  life  are  not  only  far  more  com- 
plex than  those  of  dead  matter,  but  the  conditions  of  life 
are  so  nicely  adjusted,  the  equilibrium  of  forces  so  deli- 
cately balanced,  that,  when  we  attempt  to  introduce  our 
clumsy  hands  in  the  way  of  experiment,  we  are  in  danger 
of  overthrowing  the  equilibrium,  of  destroying  the  con- 
ditions of  the  experiment,  viz.,  life  ;  and  then  the  whole 
problem  falls  immediately  into  the  domain  of  chemistry. 
What  shall  we  do  ?  In  this  dilemma  we  find  that  Na- 
ture herself  has  already  prepared  for  us,  ready  to  hand, 
an  elaborate  series  of  simplified  conditions  equivalent  to 
experiments.  The  phenomena  of  life  are,  indeed,  far  too 
complex  to  be  'at  once  understood — the  problem  of  life 
too  hard  to  be  solved — in  the  higher  animals ;  but,  as  we 
go  down  the  animal  scale,  complicating  conditions  are 
removed  one  by  one,  the  phenomena  of  life  become  sim- 
pler and  simpler,  until  in  the  lowest  microscopic  cell  or 
spherule  of  living  protoplasm  we  finally  reach  the  sim- 
plest possible  expression  of  life.  The  equation  of  life  is 
reduced  to  its  simplest  terms,  and  now,  if  ever,  we  begin 
to  understand  the  true  value  of  the  unknown  quantity. 
This  is  the  natural  history  series,  or  Taxonomic  series, 
already  spoken  of  on  page  10.  Again,  Nature  has  pre- 
pared, and  is  now  preparing  daily  before  our  eyes,  an- 


RELATION   OF  AGASSIZ  TO  EVOLUTION.        41 

other  series  of  gradually  simplified  conditions.  Com- 
mencing with  the  mature  condition  of  one  of  the  higher 
animals — for  example,  man — and  going  backward  along 
the  line  of  individual  history  through  the  stages  of  in- 
fant embryo,  egg  and  germ,  we  find  again  the  phenomena 
of  life  becoming  simpler  and  simpler,  until  we  again 
reach  the  simplest  conceivable  condition  in  the  single 
microscopic  cell  or  spherule  of  living  protoplasm.  This, 
as  already  explained,  is  the  embryonic  or  Ontogenic  se- 
ries. Again,  that  there  be  no  excuse  for  man's  ignorance 
of  the  laws  of  life,  Nature  has  prepared  still  another 
series  ;  and  this  the  grandest  of  all,  for  it  is  the  cause  of 
both  the  others.  Commencing  with  the  plants  and  ani- 
mals of  the  present  epoch,  and  going  back  along  the 
track  of  geological  times,  through  Cenozoic,  Mesozoic, 
Palaeozoic,  Eozoic,  to  the  very  dawn  of  life — the  first 
syllable  of  recorded  time — and  we  find  again  a  series  of 
organic  forms  growing  simpler  and  simpler,  until,  if 
we  could  find  the  very  first,  we  would  undoubtedly 
again  reach  the  simplest  condition  in  the  lowest  con- 
ceivable forms  of  life.  This,  as  we  have  already  seen, 
is  the  geologic  or  evolution,  or  Phylogenic  series.  We 
have  already  explained  these  three  series,  only  in  this 
connection  it  suits  our  purpose  to  take  the  terms  back- 
ward. 

Now,  it  is  by  compariso?i  of  the  terms  of  each  of  these 
series  going  up  and  down,  and  watching  the  first  appear- 
ance, the  growth,  and  the  perfecting  of  tissues,  organs, 
functions,  and   by  the   comparison   of   the   three   series 


42  WHAT.  IS  EVOLUTION? 

with  one  another  term  by  term  —  I  say  it  is  wholly  by 
comparison  of  this  kind  that  biology  has  in  recent  times 
become  a  true  inductive  science.  This  is  the  ''method 
of  comiKirison.^^  It  is  the  great  method  of  research  in 
all  those  departments  which  can  not  be  readily  managed 
by  the  method  of  experiment.  It  has  already  regenerated 
biology,  and  is  now  applied  with  like  success  in  sociology 
under  the  name  of  historic  method.  Yes ;  anatomy  be- 
came scientific  only  through  comparative  anatomy,  physi- 
ology through  comparative  physiology,  and  embryology 
through  comparative  embryology.  May  we  not  add,  soci- 
ology will  become  truly  scientific  only  through  compara- 
tive sociology,  and  psychology  through  comparative  psy- 
chology ? 

Now,  while  it  is  true  that  this  method,  like  all  other 
methods,  has  been  used,  from  the  earliest  dawn  of 
thought,  in  a  loose  and  imperfect  way,  yet  it  is  only  in 
very  recent  times  that  it  has  been  organized,  systema- 
tized, perfected,  as  a  true  scientific  method,  as  a  great 
instrument  of  research  ;  and  the  prodigious  recent  ad- 
vance of  biology  is  due  wholly  to  this  cause.  Now, 
among  the  great  leaders  of  this  modern  movement,  Agas- 
siz  undoubtedly  stands  in  the  very  first  rank.  I  must 
try  to  make  this  point  plain,  for  it  is  by  no  means  gen- 
erally understood. 

Cuvier  is  acknowledged  to  be  the  great  founder  of 
comparative  anatomy.  He  it  was  that  first  perfected  the 
method  of  comparison,  but  comparison  only  in  one  series 
— the  Taxonomic.     Von  Baer  and  Asrassiz  added  to  this, 


RELATION   OF  AGASSIZ  TO  EVOLUTION.         43 

comparison  in  the  ontogeni'c  series  also,  and  comparison 
of  these  two  series  with  each  other,  and  therefore  the 
application  of  embryology  to  the  classification  of  animals. 
If  Von  Baer  was  the  first  announcer,  Agassiz  was  the 
first  great  practical  worker  by  this  method.  Last  and 
most  important  of  all,  in  its  relation  to  evolution,  Agas- 
siz added  comparison  in  the  'geologic  or  pJiylogenic  series. 
The  one  grand  idea  underlying  Agassiz's  whole  life-work 
was  the  essential  identity  of  the  three  series,  and  there- 
fore the  light  which  they  must  shed  on  one  another. 
The  two  guiding  and  animating  principles  of  his  scien- 
tific work  were — 1.  That  the  embryonic  development  of 
one  of  the  higher  representatives  of  any  group  repeated 
in  a  general  w^ay  the  terms  of  the  Taxonomic  series  in 
the  same  group,  and  therefore  that  embryology  furnished 
the  key  to  a  true  classification  ;  and,  2.  That  the  succes- 
sion of  forms  and  structure  in  geological  times  in  any 
group  is  similar  to  the  succession  of  forms  and  struct- 
ure in  the  development  of  the  individual  in  the  same 
group,  and  thus  that  embryology  furnishes  also  the  key 
to  geological  succession.  In  other  words,  during  his 
whole  life,  Agassiz  insisted  that  the  laws  of  embryonic 
development  (ontogeny)  are  also  the  law^s  of  geological 
succession  (phylogeny).  Surely  this  is  the  foundation, 
the  only  solid  foundation,  of  a  true  theory  of  evolution. 
It  is  true  that  Agassiz,  holding  as  he  did  the  doctrine 
of  permanency  of  specific  tyj^es,  and  therefore  rejecting 
the  doctrine  of  the  derivative  origin  of  species,  did  not 
admit  the  causal  or  natural  relation  of  phylogenic  succes- 


44:  WHAT  IS  EVOLUTION? 

sion  to  embryonic  succession  and  taxonomic  order  as  we 
now  believe  it — it  is  true  that  for  him  the  relation  be- 
tween the  three  series  was  an  intellectual  not  a  physical 
one — consisted  in  the  preordained  plans  of  the  Creator, 
and  not  in  an}'  genetic  connection  or  inherited  property  ; 
but  evidently  the  first  and  greatest  step  was  the  discovery 
of  the  relation  itself,  however  accounted  for.  The  rest 
was  sure  to  follow. 

But  more.  Not  only  did  Agassiz  establish  the  essen- 
tial identity  of  the  geologic  and  embryonic  succession, 
the  general  similarity  of  the  two  series,  phylogenic  and 
ontogenic,  but  he  also  announced  and  enforced  all  the 
formal  laws  of  geologic  succession  (i.  e.,  of  evolution),  as 
we  now  know  them.  These,  as  already  stated  and  illus- 
trated, are  the  law  of  differentiation,  the  law  of  progress 
of  the  whole,  and  the  law  of  cyclical  movement,  al- 
though he  did  not  formulate  them  in  these  w^ords.  No 
true  inductive  evidence  of  evolution  was  possible  without 
the  knowledge  of  these  laws,  and  for  this  knowledge  we 
are  mainly  indebted  to  Asfassiz.  He  well  knew  also  that 
they  were  the  laws  of  embryonic  develo^Dment  and  there- 
fore of  evolution  ;  but  he  avoided  the  word  evolution,  as 
implying  the  derivative  origin  of  species,  and  used  in- 
stead the  word  development,  though  it  is  hard  to  see  in 
what  the  words  differ.  Thus,  it  is  evident  that  Agassiz 
laid  the  whole  foundation  of  evolution,  solid  and  broad, 
but  refused  to  build  any  scientific  structure  on  it ;  he  re- 
fused to  recognize  the  legitimate,  the  scientifically  neces- 
sary outcome  of  his  own  work.    Nevertheless,  without  his 


EELATION   OF  AGASSIZ  TO  EVOLUTION.        45 

work  a  scientific  theory  of  eyolution  would  have  been 
impossible.  Without  Agassiz  (or  his  equivalent),  there 
would  have  been  no  Darwin. 

There  is  something  to  us  supremely  grand  in  this  re- 
fusal of  Agassiz  to  accept  the  theory  of  eyolution.  The 
opportunity  to  become  the  leader  of  modern  thought, 
the  foremost  man  of  the  century,  was  in  his  hands,  and 
he  refused,  because  his  religious,  or,  perhaps  better,  his 
philosophic  intuitions,  forbade.  To  Agassiz,  and,  in- 
deed, to  all  men  of  that  time,  to  many,  alas  !  even  now, 
evolution  is  materialism.  But  materialism  is  Atheism. 
Will  some  one  say,  the  genuine  Truth-seeker  follows 
where  she  seems  to  lead  whatever  le  the  consequences'^ 
Yes ;  whatever  be  the  consequences  to  one's  self,  to  one's 
opinions,  prejudices,  theories,  philosophies,  but  not  to 
still  more  certain  truth.  Now,  to  Agassiz,  as  to  all  genu- 
ine thinkers,  the  existence  of  God,  like  our  own  exist- 
ence, is  more  certain  than  any  scientific  theory,  than  any- 
thing can  possibly  be  made  by  proof.  From  his  stand- 
point, therefore,  he  was  right  in  rejecting  evolution  as 
conflicting  with  still  more  certain  truth.  The  mistake 
which  he  made  was  in  imagining  that  there  was  any  such 
conflict  at  all.  But  this  was  the  universal  mistake  of  the 
age.  A  lesser  man  would  have  seen  less  clearly  the  higher 
truth  and  accepted  the  lower.  A  greater  man  would 
have  risen  above  the  age,  and  seen  that  there  was  no 
conflict,  and  so  accepted  both.  All  thinking  men  are 
coming  to  this  conclusion  now,  but  none  had  done  so 
then. 


46  WHAT   IS  EVOLUTION? 

Now,  then,  at  last,  the  obstacle  of  supernaturalism  in 
the  realm  of  Nature  having  been  removed  by  the  estab- 
lishment of  the  doctrine  of  correlation  of  natural  forces, 
and  the  extension  of  this  doctrine  to  embrace  also  life- 
force  ;  and  now  also  a  broad  and  firm  basis  of  carefully- 
observed  facts  and  well-established  laws  of  succession  of 
organic  forms  having  been  laid  by  Agassiz,  when  again, 
for  the  third  time,  the  doctrine  of  origin  of  species  "by 
derivation  with  modifications  "  was  brought  forward  by 
Darwin  in  a  far  more  perfect  form,  with  more  abundant 
illustrative  materials,  and  with  a  new  and  most  potent 
factor  of  modification — viz.,  divergent  variations  and 
natural  selection — it  found  the  scientific  world  already 
fully  prepared,  and  anxiously  waiting.  I  say  anxiously 
waiting — for  the  supposed  supernatural  origin  of  species 
had  been  the  one  exception  to  the  otherwise  universal 
law  of  cause  and  effect,  or  the  law  of  continuity.  It 
was  therefore  in  open  contradiction  to  the  whole  drift 
of  scientific  thought  for  five  hundred  years.  Is  it  any 
wonder,  then,  that  the  derivative  origin  of  species  was 
welcomed  with  joy  by  the  scientific  world  ?  For  five 
hundred  years,  scientific  thought,  like  a  rising  tide 
which  knows  no  ebb,  had  tended  thitherward  with  ever- 
increasing  pressure,  but  kept  back  by  the  one  supposed 
fact  of  the  supernatural  origin  of  species.  Darwin  lifted 
the  gate,  and  the  in-rushing  tide  flooded  the  whole  do- 
main of  thought. 

What,  then,  is  the  place  of  Agassiz  in  biological  sci- 
ence ?    What  is  the  relation  of  Agassiz  to  Darwin — of 


KELATION   OF  AGASSIZ  TO  EVOLUTIOX.        47 

Agassizian  development  to  Darwinian  evolution  ?  I  an- 
swer, it  is  the  relation  of  formal  science  to  physical  or 
causal  science.  Agassiz  advanced  bialogy  to  the  formal 
stage  ;  Darwin  carried  it  forward,  to  some  extent  at 
least,  to  the  physical  stage.  All  true  inductive  sciences 
in  their  complete  development  pass  through  these  two 
stages.  Science  in  the  one  stage  treats  of  the  laws  of 
phenomena  ;  in  the  other,  of  the  causes  or  exjolanation  of 
these  laws.  The  former  must  precede  the  latter,  and 
form  its  foundation ;  the  latter  must  follow  the  former, 
and  constitute  its  completion.  The  change  from  the  one 
to  the  other  is  always  attended  with  prodigious  impulse 
to  science. 

To  illustrate  :  Until  Kepler,  astronomy  was  little  more 
than  an  accumulation  of  disconnected  facts  concerning 
celestial  motions — abundant  materials,  but  no  science  ; 
piles  of  brick  and  stone,  but  no  building.  Kepler  re- 
duced this  chaos  to  beautiful  order  and  musical  harmony 
by  the  discovery  of  the  three  great  laws  which  bear  his 
name,  and  therefore  he  has  been  justly  called  the  legis- 

1 

lator  of  the  heavens — the  laivgiver  of  space.  But,  had 
he  been  asked  the  cause  of  these  beautiful  laws,  he  could 
only  have  answered,  '^  The  first  cause — the  direct  will 
of  the  Deity."  A.  good  answer  and  a  true,  but  not  sci- 
entific ;  because  it  places  the  question  beyond  the  do- 
main of  science,  which  deals  only  with  second  or  physical 
causes.  But  Newton  comes  forward  and  gives  a  physical 
cause.  He  shows  that  all  these  beautiful  laws  are  the 
necessary  result  of  gravitation  ;  and  thus  astronomy  be- 


48  WHAT  IS  EyOLUTIO:^'? 

comes  a  physical  science.  So,  until  Agassiz,  the  facts  of 
geological  succession  of  organic  forms  were  in  a  state  of 
lawless  confusion.  Agassiz  by  establishing  the  three  great 
laws  of  succession,  which  ought  to  bear  his  name,  re- 
duced this  chaos  to  order  and  beauty  ;  and,  therefore,  he 
might  justly  be  called  the  legislator  of  geological  history 
— the  lawgiver  of  time.  But,  when  asked  the  cause  of 
these  laws,  he  could  only  answer,  and  did  indeed  an- 
swer, '^The  plans  of  the  Creator."  A  noble  answer  and 
true,  but  not  scientific.  Darwin  now  comes  forward  and 
gives,  partly  at  least,  the  cause  of  these  laws.  He  shows 
that  all  these  beautiful  laws  are  explained  by  the  doc- 
trine of  *^  origin  of  species  by  derivation  with  modifica- 
tions " ;  that  these  laws  are  not  ultimate,  but  derivative 
from  more  fundamental  laws  of  life  ;  and  thus  biology  is 
advanced  one  step,  at  least,  toward  the  causal  stage. 
Newton  and  Darwin  substituted  second  causes  for  first 
cause — natural  for  supernatural.  They  each  in  his  own 
department  broke  the  bonds  of  supernaturalism  in  the 
domain  of  Nature. 

One  more  important  reflection  :  There  are  two,  and 
only  two,  fundamental  conditions  of  material  existence — 
space  and  time.  There  are,  therefore,  two,  and  only  two, 
cosmoses  —  space-cosmos  and  time-cosmos.  These  have 
been  redeemed  from  confusion  and  reduced,  to  law  and 
order  and  beauty — changed  from  chaos  to  cosmos — ^by 
science.  For  this  result  we  are  chiefly  indebted,  in  the 
one  case,  to  Kepler  and  Newton ;  in  the  other,  to  Agassiz 
and  Darwin.     The  universal  law,  in  the  one  cosmos,  is 


RELATION   OF   AGASSIZ  TO   EVOLUTIOX.         49 

the  law  of  gravitation ;  in  the  other,  the  law  of  evolution. 
Traced  by  analysis  to  its  deepest  roots  of  philosophic 
truth,  the  one  law  may  be  called  the  divine  mode  of  sus- 
tentation  ;  the  other,  the  divine  process  of  creation. 

Or  again  :  we  have  all  heard  of  the  '^  music  of  the 
spheres  " — a  beautiful  and  significant  name  used  by  the 
old  thinkers  for  the  divine  order  of  the  universe — a 
music  heard  not  by  human  ear,  but  only  by  the  atten- 
tive human  spirit.  Harmonic  relation  apprehended  by 
reason  we  call  Law,  and  its  embodiment  Science  ;  the 
same  apprehended  by  the  imagination  and  aesthetic 
sense,  we  call  Beauty,  and  its  embodiment  Art,  music. 
Now,  in  music  there  are  two  kinds  of  harmony,  simul- 
taneous and  consecutive — chordal  harmony  and  melody. 
These  must  be  combined  to  produce  the  grandest  effect. 
So  in  cosmic  order,  too,  there  are  two  kinds  of  harmonic 
relation — the  co-existent  in  space  and  the  consecutive  i7i 
time.  The  law  of  gravitation  expresses  the  universal 
harmonic  inter-relation  of  objects  co-existent  in  space, 
the  law  of  evolution,  the  universal  harmonic  relation  of 
for 7ns  successive  in  time.  Of  the  divine  spheral  music, 
the  one  is  the  chordal  harmony,  the  other  the  consecutive 
harmony  or  melody.  Combined  they  form  the  divine 
chorus  which  *^  the  morning  stars  sang  together." 


PART    II. 

EVIDENCES  OF  THE  TRUTH  OF 
EVOLUTION. 


CHAPTER  I. 

GEXEEAL    EVIDEI^CES    OF    EV0LUTI0:N^    AS    A    UNIVERSAL 

LAW. 

Let  us  again  remind  the  reader  that  evolution  means, 
first  of  all,  continuity.  The  law  of  evolution,  although 
it  doubtless  means  much  more,  means,  first  of  all,  a  law 
of  continuity,  or  causal  relation  tlirougliout  Nature.  It 
means  that,  alike  in  every  department  of  Nature,  each 
state  or  condition  grew  naturally  out  of  the  immediately 
preceding.  In  a  word,  it  means  that,  in  the  course  of 
Nature,  nothing  appears  suddenly  and  without  natural 
cause,  but,  on  the  contrary,  everything  is  the  natural  and 
usually  the  gradual  outcome  of  a  previous  condition. 
This  is  noifj  admitted  by  every  one  in  regard  to  nearly 
everything :  evolutionists  apply  it  to  the  whole  course  of 
Nature.  I  said  this  is  noio  admitted  by  every  one  in 
regard  to  nearly  everything  ;  but  this  has  not  always 
been  so.  The  world  has  come  to  its  present  position  on 
this  subject  only  by  a  very  gradual  process.  Let  us  then 
trace  rapidly  the  history  of  the  gradual  change,  for  it 
will  prepare  us  for  much  that  follows. 

There  was  a  time  (and  thai^not  many  decades  ago) 


54  EVIDENCES  OF  THE  TRUTH  OF  EVOLUTION. 

when  all  things,  the  origin  of  which  transcends  our  ordi- 
nary experience,  were  supposed  to  have  originated  sud- 
denly and  without  natural  process — to  have  been  made 
at  once,  out  of  hand.  There  was  a  time  when,  for  ex- 
ample, mountains  were  supposed  to  have  been  made  at 
once,  with  all  their  diversified  forms,  of  beetling  cliffs  and 
thundering  waterfalls,  or  gentle  slopes  and  smiling  val- 
leys, just  as  we  now  find  them.  But  noiu  we  know  that 
they  have  become  so  only  by  a  very  gradual  process,  and 
are  still  changing  under  our  very  eyes.  In  a  word,  they 
have  been  formed  by  a  process  of  evolution.  "We  know 
now  the  date  of  mountain-births  ;  we  trace  their  growth, 
maturity,  decay,  and  death ;  and  find  even,  as  it  were,  the 
fossil  bones  of  extinct  mountains  in  the  crumjDled  strata 
of  their  former  places.  There  was  a  time  when  continents 
and  seas,  gulfs,  bays,  and  rivers,  were  suj)posed  to  have 
originated  at  once,  substantially  as  we  now  see  them. 
Now,  we  know  that  they  have  been  changing  throughout 
all  geological  time,  and  are  still  changing.  Not,  however, 
change  back  and  forth  in  any  direction  indifferently  and 
without  goal,  but  gradual  change  from  less  perfect  to 
more  perfect  condition,  with  more  and  more  comj^lex  in- 
ter-relations— i.  e.,  by  2b  process  of  evolution.  We  are  able 
now,  though  still  imperfectly,  to  trace  some  of  the  stages 
of  this  evolution.  There  was  a  time  when  rocks  and 
soils  were  supposed  to  have  been  always  rocks  and  soils  ; 
when  soils  were  regarded  as  an  original  clothing  made  on 
purpose  to  hide  the  rocky  nakedness  of  the  new-born 
earth.    God  clothed  the  earth  so,  and  there  an  end.    Now 


GENERAL  EVIDENCES   OF  EVOLUTION.  55 

we  know  that  rocks  rot  down  to  soils  ;  soils  are  carried 
down  and  deposited  as  sediments  ;  and  sediments  re- 
consolidate  as  rocks — the  same  materials  being  worked 
over  and  over  again,  passing  through  all  these  stages 
many  times  in  the  history  of  the  earth.  In  a  word, 
there  was  a  time  when  it  was  thought  that  the  earth 
with  substantially  its  present  form,  configuration,  and 
climate,  was  made  at  once  out  of  hand,  as  a  fit  habitation 
for  man  and  animals.  Now  we  know  that  it  has  been 
changing,  preparing,  becoming  what  it  is  by  a  slow  pro- 
cess, through  a  lapse  of  time  so  vast  that  the  mind  sinks 
exhausted  in  the  attempt  to  grasp  it.  It  has  become 
what  it  now  is  by  a  process  of  evolution.  The  same 
change  of  view  has  taken  place  concerning  the  origin  of 
all  the  heavenly  bodies.  We  may,  therefore,  confidently 
generalize — we  may  assert  without  fear  of  contradiction 
that  all  inorganic  forms,  without  exception,  have  origi- 
nated by  a  process  of  evolution. 

The  proof  of  all  this  we  owe  to  geology — a  science 
born  of  the  present  century.  This  science  establishes 
the  law  of  universal  continuity  of  events,  through  infi- 
nite time,  as  astronomy  does  that  of  universal  inter-rela- 
tion of  objects  through  infinite  space.  How  great  the 
change  these  two  sciences  have  made  in  the  realm  of 
human  thought !  Until  the  birth  of  modern  astronomy 
the  intellectual  space-Jiorizon  of  the  human  mind  was 
bounded  substantially  by  the  dimensions  of  our  earth  ; 
sun,  moon,  and  stars,  being  but  inconsiderable  bodies 
circulating  at  a  little  distance  about  the  earth,  and  for 


56    EVIDEN"CES   OF  THE  TRUTH   OF  EVOLUTION". 

our  behoof.  Astronomy  was  then  but  the  geometry  of 
the  curious  lines  traced  by  these  wandering  fires  on  the 
concave  blackboard  of  heaven.  With  the  fiist  glance 
through  a  telescope  the  phases  of  Venus  and  the  satellites 
of  Jupiter,  revealed  clearly  to  the  mind  the  existence  of 
other  worlds  besides  and  like  our  own.  In  that  moment 
the  idea  of  infinite  space,  full  of  worlds  like  our  own,  was 
for  the  first  time  completely  realized,  and  became  thence- 
forward the  heritage  of  man.  In  that  moment  the  intel- 
lectual horizon  of  man  was  infinitely  extended.  So  also 
until  the  birth  of  geology,  about  the  beginning  of  the 
present  century,  the  intellectual  time-horizo7i  of  the 
human  mind  was  bounded  by  six  thousand  years.  The 
discovery  about  that  time  of  vertebrate  remains,  all 
wholly  different  from  those  now  inhabiting  the  earth, 
revealed  the  existence  of  other  time-faunas,  besides  our 
own  and  the  idea  of  infinite  time,  of  which  the  life  of 
humanity  is  but  an  epoch,  w^as  born  in  the  mind  of 
man  ;  and  again  the  intellectual  horizon  of  man  was 
infinitely  extended.  These  two  are  the  grandest  ideas, 
and  their  introduction  the  grandest  epochs,  in  the  intel- 
lectual history  of  man.  We  have  long  ago  accepted  and 
readjusted  our  mental  furniture  to  the  requirements  of 
the  one,  but  the  necessary  readjustment  to  the  other  is 
not  3"et  complete. 

All  inorganic  forms,  then,  it  is  admitted,  have  come 
by  evolution.  But  how  is  it  with  organic  or  living 
forms  ?    Let  us  see. 

Every   one   knows,    because   it   is  within  the  limits 


GENERAL  EVIDENCES   OF  EVOLUTION.  57 

of  ordinary  experience,  that  every  individual  organism 
now  originates  and  gradually  becomes  what  we  see  it,  by 
a  natural  process — that  is,  by  evolution.  If,  then,  there 
be  any  exception,  it  must  be  only  i\\e  first  of  each  kind. 
But  what  kind  ?  There  are  many  kinds  of  kinds  ;  classes, 
orders,  families,  genera,  species,  varieties.  Now,  many 
of  these  kinds  can  be  shown  to  have  become  what  we  see 
them  by  a  gradual  process  similar,  at  least,  to  evolution. 
Take  for  example,  classes.  The  class  of  fishes  and  the 
class  of  reptiles  are  now  widely  distinct  and  have  little  in 
common  except  a  vertebrate  structure  ;  but,  as  already 
shown,  page  12,  this  extreme  difference  has  not  always 
existed.  On  the  contrary,  the  earliest  representatives  of 
these  two  classes  so  merged  into  one  another  that  each 
seemed  either.  From  this  common  stock  the  two  classes 
were  gradually  separated,  each  going  its  own  way  and  be- 
coming more  and  more  widely  distinct  even  to  the  pres- 
ent day.  There  can  be  no  doubt,  therefore,  that  these  tivo 
classes,  as  we  now  know  them,  have  lecome  what  they  are 
by  a  gi'adual  process.  Again  :  In  the  whole  realm  of 
Nature  there  is  not  a  class  more  distinctly  separate  from 
every  other  and  without  intermediate  links  than  birds. 
But  this  has  not  always  been  so.  They  have  gradually 
become  so.  The  earliest  birds  were  so  reptilian  in  struct- 
ure and  appearance  that  if  we  could  see  them  now  we 
would  be  in  doubt  whether  we  should  call  them  birds  or 
reptiles.  Birds  have  gradually  separated  themselves  from 
the  reptilian  stem,  becoming  more  and  more  bird-like 
from  age  to  age,  until  now,  at  last,  the  two  classes  are 


58    EVIDENCES  OF  THE  TRUTH.  OF  EVOLUTION. 

wholly  separated  and  the  intermediate  links  destroyed. 
So  far  as  external  eharacters  are  concerned,  birds  may  be 
said  to  have  finally  and  wholly  released  themselves  from 
entangling  alliance  with  any  other  class. 

Classes,  then,  it  will  be  admitted,  have  undoubtedly 
become  what  we  now  know  them  by  a  very  gradual  pro- 
cess following  laws  identical  (as  we  have  already  seen, 
page  19)  with  the  laws  of  evolution.  Shall  we  try  or- 
ders ?  Of  the  class  Mammalia  there  are  two  well-rec- 
ognized and  widely-distinct  orders,  viz.,  the  Carnivores 
and  the  Herbivores.  We  all  know  how  widely  diverse 
these  are  in  form,  in  structure,  in  habits,  and  in  food. 
Has  it  always  been  so  ?  Have  these  been  made  so  at 
once  ?  By  no  means.  They  have  gradually  become  so. 
The  earliest  mammals  were  neither  the  one  nor  the  other 
distinctively.  They  were  omnivores,  completely  interme- 
diate in  food,  habits,  form,  and  structure.  From  this 
common  stock  the  two  orders  have  gradually  separated, 
the  carnivores  becoming  more  and  more  adapted  to  one 
mode  of  life  and  the  herbivores  to  another,  by  a  process 
following  the  laws  of  evolution,  as  already  explained. 
Shall  we  try  families  and  genera  ?  Marsh  and  Huxley 
have  shown  us  how  completely  the  horse  family  {EquidcB) 
and  the  horse-genus  (Equus)  illustrate  the  process  of 
gradual  becoming  and  the  law  of  evolution.  Under  their 
guidance,  we  see  that  the  earliest  traceable  ancestor  of 
the  horse  family,  before  it  was  distinctively  a  horse  fam- 
ily at  all,  had  on  the  fore-foot  five  toes  in  the  Lower 
Eocene,  four  toes  in  the  Upper  Eocene,  and  three  toes  in 


GENERAL  EVIDENCES   OF  EVOLUTION.  59 

the  Miocene  ;  then  we  see  the  two  side-toes  shortening  up 
more  and  more  in  the  Pliocene  and  becoming  rudiment- 
ary splints,  leaying  only  one  toe  in  the  Quaternary  and 
present  epochs.  Thus,  the  side-splints  in  the  foot  of  the 
modern  horse  tell  the  story  of  its  three-toed  ancestry. 
Similar  gradual  changes  are  clearly  traceable  in  size, 
shape,  structure  of  limbs,  of  teeth,  and  of  brain.  In  all 
respects  the  members  of  the  horse  family  have  become 
more  and  more  horse-like  in  the  course  of  time. 

This  subject  will  be  taken  up  and  more  fully  illus- 
trated, under  the  head  of  special  evidences,  in  a  subse- 
quent chapter.  We  here  touch  it  only  sufiSciently  to 
illustrate  this  universal  law  of  gradual  becoming. 

We  have  taken  only  a  few  examples,  but  the  same  is 
undoubtedly  true  of  all  Taxonomic  groups  above  species. 
Passing  over  these  last  for  the  moment,  we  take  next  races 
and  varieties.  These  smaller  groups  are  admitted  by  all 
to  be  formed  by  a  natural  process,  because  not  only  can 
we  make  them  artificially,  but  all  the  intermediate  links 
may  be  found  in  Nature.  So  we  have  only  species  re- 
maining. Yes;  species  are  imagined  by  the  old-school 
naturalist  and  by  the  anti-evolutionist  of  to-day  as  the 
ultimate  elements  of  Taxonomy.  This,  then,  is  the  last 
ditch  upon  which  the  defense  of  sui^ernaturalisni  in  the 
realm  of  Nature  is  made.  "Other  groups,"  they  say, 
"may  have  gradually  become  what  they  now  are  by  the 
successive  introduction  of  specific  forms  according  to  a 
preordained  plan  which  is  well  expressed  by  the  formal 
laws  of  evolution.      But  species  are  without  transition 


60    EVIDENCES   OF  THE   TRUTH  OF  EVOLUTION". 

forms.  They  come  in  suddenly,  remain  unchanged  while 
they  continue,  and  finally  pass  out  suddenly,  so  far  as 
specific  characters  are  concerned.  Kew  species  come  in 
their  places  by  direct  act 'of  creation — by  suhstitutioiij 
not  by  transmutation."  This,  then,  is  the  last  intrench- 
ment.  Can  we  give  any  good  evidence  of  gradual  forma- 
tion of  species  ?     I  believe  we  can. 

First,  then,  it  is  admitted  that  we  can  easily  make 
varieties  and  races  artificially.  "We  will  not  7ioiv  describe 
the  process;  we  are  all  familiar  with  the  results,  viz., 
the  varieties  of  domestic  animals  and  of  useful  and  orna- 
mental plants  ;  the  extremely  different  breeds  of  horses, 
cattle,  sheep,  dogs,  pigeons,  etc.  ;  of  wheat,  cabbages, 
turnips ;  of  roses,  dahlias,  etc.,  etc.  No  one  will  doubt 
that  the  extreme  varieties  of  any  of  these,  say  greyhound 
and  pug,  if  wild,  would  be  called  distinct  species,  or 
even  distinct  genera.  We  do  not  call  them  so,  for  two 
reasons  :  first,  because  we  see  them  made ;  and,  second, 
because  we  find  all  intermediate  links  between  them ; 
and  the  usual  definition  of  species  is  that  they  can  not 
be  made,  and  they  have  no  intermediate  links.  Thus, 
then,  the  question  is  narrowed  down  to  wild  species. 
They  say  :  **We  take  our  stand  on  these"  (surely  a  very 
narrow  ground  for  so  broad  a  philosophy).  ''We  defy 
you  to  show  gradual  formation  with  intermediate  links." 

Now,  in  fact,  by  diligent  search  such  intermediate 
links  between  well-recognized  species  have  been  found  in 
some  cases,  especially  in  birds,  on  account  of  their  great 
power  of  dispersal.    Certain  forms  have  long  been  known 


GENERAL  EVIDENCES   OF  EVOLUTION.  61 

from  widely-separated  regions,  and  universally  regarded 
as  distinct  species,  as  distinct  as  any.  Then,  by  minute 
examinations  of  intermediate  regions,  a  complete  series  of 
intermediate  forms  has  been  picked  up.  This  has  oc- 
curred not  only  in  one  case  but  in  many  cases,  and  not 
in  birds  only  but  in  many  other  classes — examples  in- 
crease with  our  increasing  knowledge.*  The  only  answer 
to  such  eyidence  is  that  these  are  not  true  species,  Now, 
see  the  fallacy  lurking  here  !  They  define  species  as  ul- 
timate elements  of  taxonomy,  as  distinct  and  without 
intermediate  links,  and  then  require  us  to  find  such  in- 
termediate links ;  and,  finally,  when  with  infinite  pains 
some  such  links  are  found,  they  say :  "  Oh  !  I  see ;  we 
were  mistaken ;  they  are  only  varieties  !  ! "  It  is  true 
that  naturalists,  when  intermediate  links  are  found,  usu- 
ally put  all  together  as  one  species,  but  this  they  do 
purely  for  the  sake  of  clearness  of  definition  and  descrip- 
tion. It  is  freely  admitted  by  the  evolutionist  that  spe- 
cies are  7ioio  usually  distinct  and  without  intermediate 
links,  these  having  been  destroyed  in  the  struggle  for 
life.  This  will  be  fully  explained  in  another  chapter. 
It  is  also  freely  admitted  that  although  intermediate 
links  must  have  existed  at  one  time,  their  remains  are 
rarely  found.  The  reason  of  this  will  also  be  explained 
hereafter.  Nevertheless,  in  some  cases,  as  already  seen, 
we  do  find  them  still  existing.  Now,  we  add  that  in 
some  cases,  where  they  no  longer  exist;  we  find  them  in 

*  Cope,  "Science,"  vol.  ii,  p.  274,  1883. 


62    EVIDENCES  OF  THE  TRUTH   OF  EVOLUTION. 

the  form  of  fossil  remains.  The  most  remarkable  exam- 
ple of  this  is  found  in  the  gradual  changes  in  the  forms 
of  Planorbis  in  the  fresh-water  deposits  of  Steinheim^  as 
shown  by  the  admirable  researches  of  Hyatt.*  We  shall 
discuss  these  also  more  fully  in  another  place.  ISTow,  if 
there  be  any  such  links  at  all,  however  rare,  then  every 
objection  to  the  derivative  origin  of  species  is  removed. 
Perhaps  it  may  be  well  to  make  bare  mention  of 
another  kind  of  evidence,  viz.,  the  actual  change  of  spe- 
cies under  the  eyes,  by  the  action  of  change  of  environ- 
ment. The  different  species  of  the  genus  Artemia  (a  low 
form  of  crustacean)  live  in  brine-pools.  By  concentrat- 
ing the  brine  of  such  a  pool,  one  species  {A.  salino)  has 
been  observed  to  change  in  successive  generations  into 
another  {A,  Muhlhausenii),  and  the  latter  back  again  to 
the  former  by  slow  freshening,  f  Again  :  The  siredon 
and  the  amblystoma  have  always,  until  recently,  been  re- 
garded as  not  only  distinct  species,  but  distinct  genera 
of  amphibians.  Siredon  was  supposed  to  be  a  permanent 
gill-breather,  while  amblystoma  becomes  by  metamorjoho- 
sis  a  pure  air-breather.  Now,  however,  it  is  known  that 
the  former  mav  chansre  into  the  latter.  But  the  most 
curious  part  of  the  life-history  of  these  animals,  is  that 
if  water  be  abundant  the  siredon  reproduces  freely,  and 
remains  indefinitely  a  gill-breather  ;  but  if  the  water 
dries  up  it  changes  into  the  lung-breathing  amblystoma. 

*  Boston   Society  of  Natural  History  —  anniversary  memoir,   1880. 
Also,  "  American  Naturalist,"  June,  1882. 
f  "Archives  des  Sciences,"  vol.  liv,  1875. 


GENERAL  EVIDENCES   OF  EVOLUTION.  63 

We  do  not  give  this  as  examples  of  change  of  species, 
for  the  change  is  in  the  individual  life,  and  therefore  in 
the  nature  of  metamorphosis,  but  as  evidence  of  the 
power  of  physical  conditions  in  modifying  the  develop- 
ment of  organic  forms  and  therefore  of  the  manner  in 
which  gill-breathers  were  j^robably  transformed  into  air- 
breathers. 

To  sum  ujo :  1.  All  inorganic  forms,  without  excep- 
tion, have  become  what  we  find  them  by  a  natural  pro- 
cess— i.  e.,  by  evolution.  2.  All  organic  or  living  forms 
within  the  limits  of  observation,  i.  e.,  every  living  thing, 
has  become  what  we  now  see,  by  a  gradual,  natural  pro- 
cess— i.  e.,  by  evolution.  3.  All  taxonomic  groups,  except 
species,  have  undoubtedly  become  what  we  now  see  them 
by  a  gradual  process,  following  the  laws  of  evolution,  and 
therefore  presumably  by  a  natural  process  of  evolution. 
4.  By  artificial  means,  breeds,  races,  etc.,  very  similar, 
at  least  in  many  respects,  to  species,  are  seen  to  arise  by  a 
gradual  natural  process — i.  e.,  by  evolution.  5.  In  some 
instances,  at  least,  natural  species  are  observed  to  j^ass 
into  one  another  by  intermediate  links  in  such  wise  that 
we  are  forced  to  conclude  that  they  have  been  formed  by 
a  natural  process. 

May  we  not,  then,  safely  generalize,  and  make  the 
law  universal  ?  Is  not  this  a  sufficient  ground  for  confi- 
dent induction  ?  Even  though  some  facts  are  still  inex- 
plicable, is  that  a  sufficient  reason  for  withholding  assent 
to  a  theory  which  explains  so  much  ?  In  all  induction 
we  first  establish  a  law  provisionally  from  the  observation 


64    EYIDENCES   OF  THE  TRUTH  OF  EYOLUTIO^^. 

of  a  comparatively  few  facts,  and  then  extend  it  over  a 
multitude  of  facts  not  included  in  the  original  induction. 
If  it  explains  these  also,  the  law  is  verified.  The  law  of 
gravitation  was  first  based  on  the  observation  of  a  few 
facts,  and  then  verified  by  its  explanation  of  nearly  all 
the  facts  of  celestial  motion.  There  are  some  outstand- 
ing facts  of  celestial  motion  still  unexplained,  but  we  do 
not,  therefore,  doubt  the  law  of  gravitation.  The  same 
principle  applied  in  biology  ought  to  establish  the  law  of 
evolution,  for  it  also  explains  all  the  facts  of  biology  as 
no  other  law  can.  But  inductive  evidence  differs  from 
other  kinds  of  evidence  in  one  respect,  which,  in  fact, 
constitutes  its  strength  to  the  scientific,  but  its  weakness 
to  the  popular  mind.  It  is  a  kind  of  circumstantial  evi- 
dence, but  its  force  does  not  consist  in  a  few  strong  cir- 
cumstances easily  appreciated,  such  as  strike  the  popular 
mind,  and  force  conviction,  but  rather  in  a  multitude  of 
small  circumstances,  each  by  itself  insignificant,  but  all 
together  pointing  to  one  conclusion  and  demanding  one 
explanation.  Such  evidence  is,  indeed,  overwhelming, 
but  only  to  the  mind  that  masters  it.  The  evidence  for 
the  law  of  gravitation  is  literally  the  whole  science  of  as- 
tronomy. So  also  the  evidence  for  the  law  of  evolution  is 
the  whole  science  of  biology.  Neither  of  these  laws  can 
be  proved  in  a  debating  society,  but  only  by  a  course  of 
study.  In  the  one  case  the  law  has  been  universally  ac- 
cepted— not,  however,  on  evidence,  for  there  are  few  in- 
deed who  appreciate  the  evidence,  but  on  the  authority 
of  scientific  unanimity.     In  the  other  case  there  has  not 


GENERAL  EVIDENCES   OF  EVOLUTION.  05 

yet  been  time  enough  for  the  already  established  unanim- 
ity to  have  its  full  effect. 

Thus  much,  we  belieye,  will  be  generally  admitted  as 
a  yery  moderate  claim.  Evolution  is  certainly  a  legiti- 
mate induction  from  the  facts  of  biology.  But  we  are 
prepared  to  go  much  further.  We  are  confident  that 
evolution  is  absolutely  certain.  Not,  indeed,  evolution  as 
a  special  theory — Lamarckian,  Darwinian,  Spencerian — 
for  these  are  all  more  or  less  successful  modes  of  explain- 
ing evolution  ;  nor  evolution  as  a  school  of  thought,  with 
its  following  of  disciples — for  in  this  sense  it  is  still  in 
the  field  of  discussion — but  evolution  as  a  law  of  deri- 
vation of  forms  from  previous  forms  ;  evolution  as  a  law 
of  continuity,  as  a  universal  law  of  becoming.  In  this 
sense  it  is  not  only  certain,  it  is  axiomatic.  It  is  only 
necessary  to  conceive  it  clearly,  to  see  that  it  is  a  neces- 
sary truth.  This  may  seem  paradoxical  to  some.  I  stop 
to  justify  it. 

Physical  phenomena  we  all  admit  follow  one  another 
in  unbroken  succession,  each  derived  from  a  preceding, 
and  giving  origin  to  a  succeeding.  We  call  this  the  law 
of  causation,  and  say  that  it  is  axiomatic.  We  might  call 
it  a  law  of  derivation.  So  also  natural /orms,  organic  or 
other,  follow  one  another  in  continuous  chain,  each  de- 
rived from  a  preceding  and  giving  origin  to  a  succeeding. 
We  call  this  a  law  of  derivation.  We  might  call  it  a  laiu 
of  causation,  and  say  that  it  too  is  axiomatic.  The  ori- 
gins of  new  phenomena  are  often  obscure,  even  inexplica- 
ble, but  we  never  think  to  doubt  that  'they  have  a  natural 


QQ    EVIDENCES   OF   THE  TRUTH   OF  EVOLUTION. 

cause  ;  for  so  to  doubt  is  to  doubt  the  yalidity  of  reason, 
and  the  rational  constitution  of  Nature.  So  also  the  ori- 
gins of  new  organic  forms  may  be  obscure  or  even  inex- 
plicable, but  we  ought  not  on  that  account  to  doubt 
that  they  had  a  natural  cause,  and  came  by  a  natural 
process ;  for  so  to  doubt  is  also  to  doubt  the  validity  of 
reason,  and  the  rational  constitution  of  organic  Nature. 
The  law  of  evolution  is  naught  else  than  the  scientific  or, 
indeed,  the  rational  mode  of  thinking  about  the  origin  of 
thi^igs  in  every  department  of  Nature.  In  a  word,  it  is 
naught  else  than  the  law  of  necessary  causation  applied 
to  forms  instead  of  phenomena.  Evolution,  therefore,  is 
no  longer  a  school  of  thought.  The  words  evolutionism 
and  evolutionist  ought  not  any  longer  to  be  used,  any 
more  than  gravitationism  and  gravitationist ;  for  the  law 
of  evolution  is  as  certain  as  the  law  of  gravitation.  Nay, 
it  is  far  more  certain.  The  nexus  between  successive 
events  in  time  (causation)  is  far  more  certain  than  the 
nexus  between  coexistent  objects  in  space  (gravitation). 
The  former  is  a  7iecessary  truth,  the  latter  is  usually 
classed  as  a  contingent  truth.  I  have  used  and  may 
continue  to  use  the  term  evolutionist,  but  if  so  it  is 
only  in  deference  to  the  views  of  many  intelligent  per- 
sons, who  do  not  yet  see  the  certainty  of  the  law. 


CHAPTER  11. 

SPECIAL   PROOFS   OF   EVOLUTION". 

Introductory. 

It  will  be  seen  from  the  preceding  chapter  that  we 
regard  the  law  of  eyolution  in  its  wider  sense,  viz.,  the 
derivative  origin  of  all  forms,  organic  or  other,  as  axio- 
matic, and  therefore  requiring  no  further  proof.  Among 
scientific  men  there  is  no  longer  any  discussion  of  the 
truth  of  this  law,  but  only  of  the  theories  of  the  causes 
of  the  law.  We  believe  that  to  the  scientific  mind  there 
is  no  other  rational  mode  of  looking  at  the  subject  of 
origin  of  organic  forms.  To  such  a  mind,  therefore,  all 
that  follows  is  but  the  deductive  application  of  that  law 
in  the  explanation  of  the  phenomena  of  organic  Nature. 
But  it  takes  time  for  the  popular  mind  to  readjust  it- 
self to  new  and  revolutionary  truth.  Many  minds,  even 
among  the  most  intelligent,  have  not  yet  accepted  this  as 
the  only  rational  mode  of  thought.  Many  men  require 
iwYthev  special  proof s  oi  the  derivative  origin  of  organic 
forms.  Even  to  those  who  accept  evolution,  these  proofs 
will  be  interesting  as  illustrations  of  such  origin.     We 


68    EVIDEXCES   OF  THE   TRUTH   OF  EVOLUTION. 

will  attempt  to  bring  out  these  proofs  under  several 
Leads,  the  most  important  of  which  are  :  1.  Proofs  from 
morphology,  or  the  general  laws  of  animal  structure  ;  2. 
Proofs  from  embryology  ;  3.  Proofs  from  geographical 
distribution  of  organic  forms  ;  and,  4.  Proofs  from  artifi- 
cial breeding.  The  subject  is  so  yast  that  all  we  can  do 
is  to  touch  lightly  only  the  most  salient  points  under 
each  of  these  heads  ;  for,  as  we  have  already  said,  the  evi- 
dence is  really  nothing  less  than  the  whole  science  of 
biology.  Prej^aratory  to  this,  however,  it  is  necessary  to 
bring  out  a  little  more  fully  than  before  (page  29), 
though  still  only  in  outline,  the  two  antagonistic  views, 
which  may  be  called  the  old  and  the  new,  or  the  natural 
and  the  supernatural,  of  the  origin  of  new  organic  forms, 
especially  species. 

Origin  of  New  Organic  Forms ;  the  Old  View  briefly 
stated. — According  to  the  old-school  naturalists,  species 
are  the  ultimate  elements  of  taxonomy  :  genera,  families, 
orders,  etc.,  may  gradually  change  their  character  from 
age  to  age,  by  the  introduction  of  new  species  ;  but  spe- 
cies were  supposed  to  be  substantially  permanent.  It  was 
necessary  to  have  some  unit  for  convenience  of  descrip- 
tion and  classification,  and  this  was  found  to  be  the  best 
because  most  stable.  As  in  nearly  all  cases  of  beliefs, 
this  doctrine  was  held  at  first  somewhat  loosely,  as  a  pro- 
visional and  convenient  view — as  a  good  working  hy- 
pothesis— but  gradually,  under  pressure  of  controversy, 
became  more  strictly  formulated,  and,  as  it  were,  hard- 
ened into  a  scientific  dogma,  especially  in-  the  hands  of 


SPECIAL  PEOOFS   OF  EVOLUTION.  69 

Agassiz.  According  to  this  view,  the  first  pair  or  pairs 
of  each  specific  kind  originated  we  know  not  how,  but 
certainly  at  once  in  its  present  form  in  full  perfection, 
and,  therefore,  presumably  by  direct  creative  act  of 
Deity  ;  and  then  afterward  by  the  law  of  generation  con- 
tinued to  produce  others  of  the  same  pattern  indefinitely. 
Moreover,  the  first  one  or  more  pairs  of  each  kind  multi- 
plied and  spread  abroad  in  every  direction,  each  from  its 
own  center  of  origin,  as  far  as  physical  conditions  and 
struggle  for  life  with  other  species  would  allow.  This 
idea  explains  tolerably  well  the  geographical  distribution 
of  species  as  we  now  find  it.  For  example,  species  on 
different  continents  are  widely  different,  because  those 
on  each  have  originated  independently  where  we  now 
find  them,  and  spread  in  all  directions  as  far  as  physical 
conditions  would  allow,  but  could  not  reach  other  con- 
tinents because  of  the  ocean-barrier.  That  this  is  the 
only  reason  they  are  not  there,  is  shown  by  the  fact  that, 
if  they  are  carried  there,  they  usually  do  perfectly  well. 
Even  on  the  same  continent,  for  the  same  reason,  species 
may  be  very  different  if  separated  by  impassable  barri- 
ers such  as  high  mountain-chains  or  by  climate.  But 
wherever  one  group  of  species,  originating  in  one  place, 
comes  in  contact  on  the  margin  of  tlieir  range  with 
another  group  of  species  originating  in  another  place, 
we  see  no  evidence  of  transmutation  of  one  form  into 
another,  but  only  suistitution  of  one  fully-formed  spe- 
cies for  another  equally  fully  formed.  Therefore,  we 
must  conclude  that  physical  conditions  may  limit  the 


70     EVIDENCES   OF  THE  TRUTH   OF  EVOLUTION. 

range  of  a  species,  but  can  not  transmute  it  into  another. 
Thus,  to  say  the  least,  many  of  the  facts  of  geographical 
distribution  are  well  explained  by  this  idea  of  creative 
origin  in  specific  centers  and  subsequent  permanence  of 
specific  form.  We  say  many  of  the  facts  ;  we  will  show 
hereafter  that  not  all  can  be  thus  exj^lained. 

But  the  main  question  is  not  of  geographical  but  of 
geological  distribution  ;  not  distribution  in  space,  but 
succession  in  time.  Species  do  not  continue  forever.  On 
the  contrary,  they  have  changed  many  times  in  the 
course  of  geological  history.  As  conditions  become  un- 
favorable, species  die  out  or  become  extinct,  and  others 
take  their  place  and  carry  forward  the  life  and  develop- 
ment of  the  organic  kingdom.  Now,  how  do  they 
change  ?  According  to  this  school  of  thought,  here  also, 
as  in  geographical  distribution,  they  are  not  transmuted 
but  replaced ;  here  also  physical  conditions  may  destroy 
a  species,  but  can  not  transform  it  into  another.  As  spe- 
cies die  out,  others  are  created  at  once,  out  of  hand  and 
fully  formed  in  their  place ;  but  in  accordance  with  a 
preordained  plan  consistently  carried  out  and  working 
ever  toward  higher  and  higher  conditions.  Thus,  life  is 
continued  on  the  earth  by  the  alternation  of  supernatu- 
ral and  natural  processes  ;  by  the  alternate  use  of  direct 
and  indirect  action  of  Deitv  :  direct  in  the  introduction 
of  first  pairs,  indirect  through  the  natural  process  of  re- 
production in  the  continuance  and  multiplication  of  the 
species.  Each  sjiecies  is  made  according  to  a  pattern  in 
the -Divine  mind,  on  a  sort  of  intellectual  die,  and  then 


SPECIAL  PROOFS   OF  EVOLUTION".  71 

continues  to  reproduce  a  succession  of  individuals  of  the 
same  pattern  as  if  struck  from  the  same  die  until  the  die 
is  broken  or  worn  out.  Another  die  is  made,  of  another 
pattern,  and  individuals  are  struck  from  this  ;  and  so  on, 
throughout  the  whole  geological  history  of  the  organic 
kingdom.  Only,  we  must  add  that  the  successive  dies 
are  made  to  follow  one  another  according  to  a  plan  which 
is  expressed  by  the  three  laws  already  given  on  page  11. 
Thus,  the  origin  of  individuals  is  natural,  the  origin 
of  species  supernatural ;  the  making  of  dies  is  supernatu- 
ral, the  coinage  is  natural. 

We  have  stated  this  view  in  a  too  extreme  form,  in 
order  to  make  it  clearer.  We  now,  therefore,  proceed  to 
qualify  somewhat.  Specific  types  were  held,  by  writers 
of  this  school  of  thought,  to  be  siibstantially  but  not 
absolutely  unchangeable.  Successive  individuals  of  the 
same  species  were  admitted  to  be  not  exactly  alike. 
Such  slight  differences  were  called  varieties.  It  was  ad- 
mitted, indeed,  that  species  varied,  but  it  was  believed 
that  such  variations  in  any  direction  were  strictly  limited 
in  amount.  A  species  may  be  compared  to  a  right  cyl- 
inder standing  on  end.  As  such  a  cylinder  may  be  tilted 
slightly  in  one  direction  or  another,  without  overthrow- 
ing its  equilibrium,  the  cylinder  tending  ever  to  right 
itself  and  return  to  its  original  position,  so  a  species 
may  be  varied  slightly  in  one  direction  or  another  with- 
out destroying  its  integrity,  the  species  tending  ever  to 
return  to  its  normal  or  typical  form.  But  as  the  cylin- 
der, if  pushed  too  far  from  its  normal  position,  is  over- 


72    EVIDENCES   OF  THE  TRUTH   OF  EYOLITTrON. 

thrown,  so  also  a  species,  if  pressed  too  far  in  the  way  of 
variation  from  its  typical  form,  is  destroyed,  but  not 
changed  into  another  species.  As  cylinders  may  be  more 
or  less  rigid,  depending  upon  the  breadth  of  their  bases, 
so  also  some  species  are  more  rigidly  set  in  their  typical 
form,  and  some  are  more  plastic  to  influences  causing 
Tariations,  but  in  all  cases  there  is  a  limit  to  the  amount 
of  oscillation  consistent  with  integrity. 

The  New  View  briefly  stated. — According  to  Darwin, 
and  all  biologists  of  the  present  day,  species  are  variable 
without  limit,  if  only  the  causes  of  change  are  constant  and 
slow  enough  in  their  operation,  and  the  time  long  enough. 
A  sj)ecies  must  be  in  harmony  with  its  environment,  for 
this  is  the  condition  of  its  existence.  Now,  if  the  envi- 
ronment change,  the  species  must  tend  to  change  slowly 
from  generation  to  generation,  so  as  to  readjust  its  rela- 
tions in  harmony  with  the  changing  environment.  If 
the  change  of  environment  be  slow,  the  readjustment 
may  be  successful,  and  the  species  will  change  gradually 
into  another  form,  so  different  that  it  will  be  called  a 
different  species,  especially  if  the  intermediate  gradations 
be  destroyed.  If  the  change  in  the  environment  be  too 
rapid,  many  species,  especially  the  more  rigid,  will  be 
destroyed,  while  the  more  plastic  may  survive  by  modifi- 
cation. Thus,  at  every  step  in  the  evolution  of  the  or- 
ganic kingdom,  some  species  have  died  without  issue, 
while  others  have  saved  themselves  by  changing  into  new 
forms  in  harmony  with  the  new  environment.  Compar- 
ing to  a  growing  tree,  some  branches  overshadowed  die. 


SPECIAL  PKOOFS   OF  EVOLUTION.  73 

while  others  push  on  for  light,  forming  new  lateral  buds, 
and  dividing  as  they  grow.  By  continued  divergent 
change  species  gradually  become  genera,  genera  families, 
etc.  Thus,  varieties,  species,  genera,  families,  orders, 
classes,  etc.,  are  only  different  degrees  of  differences 
formed  all  in  the  same  way.  Varieties  are  only  com- 
mencing species,  species  commencing  genera,  and  so  on. 
There  is  no  making  and  wearing  out  of  dies,  and  making 
of  new  ones ;  the  whole  process  is  a  natural  one— the 
whole  series  is  genetically  connected.  In  a  perfect  classi- 
fication varieties,  species,  genera,  families,  orders,  classes, 
etc.,  are  only  different  degrees  of  llood-Mnsliip, 

So  much  may  be  regarded  as  certain,  and  out  of  the 
field  of  discussion  among  biologists  of  the  present  day. 
It  is  only  in  defining  this  process  more  accurately,  and 
especially  in  the  theory  of  the  causes  or  factors  of  evolu- 
tion, that  there  are  still  difference  and  discussion.  The 
most  probable  view  on  this  subject  we  now  proceed  to 
give. 

Factors  of  Evolution. — The  causes  of  change  or  adapt- 
ive modification,  or  the  factors  of  evolution,  are  at  least 
four  well  known,  and  probably  many  more  still  un- 
known :  1.  The  physical  environment — heat  and  cold, 
dryness  and  moisture — affects  function  of  organs,  and 
function  affects  structure,  and  both  changed  function 
and  changed  structure  are  inherited  by  offspring,  and 
so  increased  from  generation  to  generation,  becoming 
greater  without  limit.  2.  Increased  use  or  disuse  of 
organs  enforced  or  permitted  by  change  in  the  environ- 


74    EVIDENCES   OF  THE   TRUTH  OF  EYOLUTIOX. 

ment,  physical  or  organic,  or  both,  induces  change  iu 
form,  size,  and  structure  of  the  organs ;  and  this  change 
is  inherited  by  the  offspring,  and  so  from  generation  to 
generation  small  differences  are  integrated  until  they  be- 
come great  without  limit.  These  two  factors  were  recog- 
nized bv  Lamarck.  3.  "^N'atural  selection,"  or  ^'^ survival 
of  the  fittest,"  among  divergent  varieties  of  offspring. 
This  is  the  distinctive  Darwinian  factor.  In  the  two 
preceding  factors  the  change  is  during  the  indivichial 
lifetime,  and  reproduction  is  supposed  to  transmit  it  un- 
changed to  the  offspring.  In  this  factor,  on  the  con- 
trary, the  form  and  structure  are  supposed  to  remain  un- 
changed during  the  individual  life,  but  for  some  unknown 
cause  there  are  slight  variations  in  different  directions 
(divergent)  in  the  offspring  from  the  same  parents. 
Now,  when  we  remember  that  by  rejiroduction  the  num- 
ber of  individuals  tends  to  increase  by  geometrical  pro- 
gression, and  that  in  each  generation  only  a  very  few  (on 
an  average  only  two  from  all  the  offspring  of  one  pair) 
can  survive,  it  is  evident  that  among  these  divergent  va- 
rieties those  will  most  likely  survive  which  are  most  in 
harmony  with  the  external  environment,  and  which  pos- 
sess the  most  efficient  organs  of  defense  or  of  escape,  or 
for  food-taking.  The  surviving  offspring,  therefore,  will 
be  on  the  average  better  in  these  respects  than  their  par- 
ents. It  matters  not  how  little  better,  for  the  integration 
of  even  infinitesimal  improvements  from  generation  to 
generation  will  eventually  produce  any  required  amount 
of  change.     4.   To  the  above   Darwin  has  added  also 


SPECIAL  PROOFS   OF  EVOLUTION.  75 

**  sexual  selection."  In  7iatural  selection  there  is  struggle 
of  all  for  food,  or  means  of  livmg.  In  sexual  selection 
there  is  a  struggle  among  the  7nales  for  possession  of  the 
female,  and  the  means  of  procreation.  The  one  is  con- 
nected with  the  nutritive  appetite,  the  other  with  the 
reproductive  appetite.  This  mode  of  selection  acts  in  two 
ways,  by  the  law  of  battle  and  the  law  of  attractiveness. 
The  strongest  or  the  most  attractive  males  alone,  or 
mainly,  leave  offspring,  which,  of  course,  inherit  their 
peculiarities ;  and  these  are  increased  indefinitely  by 
integration  through  successive  generations,  thus  increas- 
ing the  strength  or  the  beauty.  Of  these  two  laws,  the 
law  of  battle  is  most  conspicuous  among  mammals,  and 
the  law  of  attractiveness  among  birds.  It  is  evident  that 
this  factor  can  not  operate  among  many  lower  animals 
which  are  hermaphroditic,  nor  among  plants. 

Of  these  acknowledged  factors  of  evolution,  the  first 
two  were  known  to  Lamarck  and  the  older  evolutionists. 
The  third  and  fourth  are  distinctively  Darwinian.  Ac- 
cording to  Darwin,  while  all  these  are  operative,  the  third 
is  the  most  powerful ;  but  Spencer  accords  this  distinc- 
tion to  the  Lamarckian  factors.  Most  American  zoolo- 
gists take  the  same  view. 

Such  until  very  recently  were  all  the  recognized  fac- 
tors of  evolution.  But,  within  the  past  year  (1886)  has 
taken  place,  it  seems  to  us,  the  most  important  advance 
in  the  theory  of  evolution  since  Darwin.  It  is  the  sugges- 
tion by  Mr.  Catchpool,  *  and  afterward  the  more  full  elab- 

*  "Nature,"  vol.  xxxi,  p.  4,  1884. 


TG    EVIDENCES  OF  THE  TRUTH  OF  EVOLUTION. 

oration  by  Dr.  Eomanes,  of  anotlier  factor,  which  he  calls 
^'physiological  selection. "  * 

The  great  objections  to  the  sufficiency  of  the  theory 
of  evolution,  as  left  by  Darwin,  were  twofold. :  1.  While 
natural  selection  accounts  completely  for  the  formation 
of  useful  structures  or  adaptive  modifications,  and 
therefore  for  differences  characterizing  classes,  orders, 
families,  and  even  genera — for  these  are  all  adaptive — 
it  can  not  so  comj^^letely  account  for  those  constitut- 
ing species  ;  for  these  consist  mostly  of  trivial  differ- 
ences in  coloration,  relative  proportion  of  parts,  which 
are  of  no  perceivahU  use  in  the  struggle  for  life,  and 
therefore  could  not  be  preserved  and  integrated  by 
natural  selection.  Therefore,  according  to  Komanes, 
natural  selection  is  a  theory  of  origin  of  adaptive  struct- 
ures rather  than  of  origin  of  species.  Comparing  to  a 
growing  tree,  once  admit  lateral  buds  started,  and  nat- 
ural selection  completely  accounts  for  the  growth  in  dif- 
ferent directions,  and  therefore  for  the  profuse  ramifica- 
tion ;  but  the  origin  of  the  lateral  buds  is  not  explained. 

2.  The  second  difficulty  is  as  follows  :  Such  com- 
mencing differences  as  constitute  varieties  and  species 
not  only  would  not  be  i)reserved  and  integrated  by  nat- 
ural selection  unless  useful,  but  would  immediately  be 
sivamped  hy  cross-hreeding  with  the  parental  form.  But, 
as  the  whole   divergence   commences   in   varieties,   evi- 

*  See  abstract  of  Dr.  Romanes's  views,  "Nature,"  vol.  xxxiv,  pp.  314, 
336,  362.  Also,  discussions  of  the  same  by  Meldola,  Galton,  Wallace, 
etc.,  in  immediately  subsequent  numbers. 


SPECIAL  PROOFS  OF  EVOLUTION.  77 

dentlj  it  could  not  commence  at  all  unless  this  cross- 
breeding be  in  some  way  prevented.  This  may,  indeed, 
be  done,  without  the  assumption  of  any  new  factor  of 
eYoliition,  hy  7)1  igr  at  ion  J  and,  hence,  migration  must  be 
regarded  as  an  important  agent  in  the  creation  of  new 
forms,  not  only  by  the  effect  of  a  new  environment,  but 
also  by  prevention  of  the  swamping  of  commencing 
species  by  cross-breeding  with  the  parental  form  ;  but  in 
a  crowded  locality,  without  outlet  for  migration  (the  very 
conditions  most  favorable  for  severe  competitive  strug- 
gle, and  therefore  for  most  potent  operation  of  natural 
selection  ;  and  therefore,  also,  according  to  Darwin,  for 
profuse  diversification),  commencing  varieties  could  not 
pass  into  species,  because  swamped  by  cross-breeding. 
Once  the  divergence  reaches  the  point  of  cross-sterility 
— i.  e.,  of  species — then,  indeed,  by  true  breeding,  charac- 
ters, even  tliough  not  useful,  may  be  preserved.  But 
how  is  it  to  commence  ? 

This  difficulty  has  been  severely  felt  by  all  Darwin- 
ists. It  seems  to  us  that  it  is  largely  met  by  Dr.  Eo- 
manes.  According  to  Romanes,  no  organ  is  so  subject 
to  varietal  changes  as  the  reproductive,  and  these  in  no 
respect  so  much  as  in  degrees  of  fertility.  Unfortunate- 
ly, these  changes  are  not  visible,  and  must  be  judged  of 
only  by  the  results.  It  is  not  uncommon,  for  example,  to 
find,  sterility  between  individuals  (sexual  incompatibility) 
who  are  both  of  them  perfectly  fertile  with  other  indi- 
viduals. Similarly,  cross-sterility,  partial  or  complete,  is 
not  uncommon  between  varieties  or  races,  as  Mr.  Darwin 


78    EVIDENCES   OF  THE  TRUTH  OF  EYOLUTIOK 

lias  long  ago  noticed.  It  very  generally,  as  we  know, 
occurs  between,  and,  in  fact,  is  constantly  used  as  a  test 
of,  si^ecies.  Now,  this  cross-sterility  with  parent  stock, 
which  we  find  so  constant  a  character  of  species,  and 
which,  therefore,  must  have  commenced  as  a  partial  cross- 
sterility  in  varieties,  is  it  antecedent  or  consequent  to 
other  variations  9  It  has  been  usual  to  suppose  it  conse- 
quent to  a  certain  amount  of  divergence,  viz.,  that  which 
constitutes,  or  at  least  approaches,  species.  But,  accord- 
ing to  Eomanes,  it  is  antecedent.  Among  many  other 
variations,  this  is  that  one  which  originates  species,  be- 
cause it  prevents  reversion  by  cross-breeding  with  the 
parent  stock,  and  insures  true  breeding  with  its  own 
kind.  In  a  word,  it  sexually  isolates  the  species.  Sup- 
pose, then,  a  species  multiplying  indefinitely  in  one  lo- 
cality :  trivial  variations  of  many  kinds,  and  in  many 
directions,  occur  among  the  offspring.  These  are  merged 
by  cross-breeding  into  the  original  type,  which,  there- 
fore, remains  unchanged.  But,  from  time  to  time,  among 
these  variations  there  occur  some  affecting  the  reproduc- 
tive organs  in  such  wise  as  to  produce  partial  or  complete 
cross-sterility  with  the  parent  form.  This  is  the  begin- 
ning of  a  new  species.  It  breeds  true  with  its  own  kind, 
and  therefore  all  the  associated  variations  external  and 
visible,  and  therefore  constituting  species,  although  triv- 
ial and  of  no  use  in  the  struggle  for  life,  are  preserved. 
This  view  completely  accounts  for  the  cross-fertility 
of  artificial  breeds  equivalent  in  other  respects  to  species  ; 
for  cross-sterility  is  not  an  end  aimed  at  by  the  breeder, 


SPECIAL  PROOFS   OF  EVOLUTION".  79 

it  being  easy  to  prevent  cross-breeding,  if  desired,  by 
artificial  isolation.  But,  if  this  yiew  be  true,  species 
from  widely-diiierent  geographical  regions  ought  also  to 
be  often  cross-fertile,  because,  having  been  formed  by 
geographical  isolation,  sexual  isolation  was  not  a  neces- 
sary factor  in  their  formation.  This  point  deserves  test- 
ing by  careful  observation. 

It  may  be,  and  has  been,  objected  to  Dr.  Eomanes's 
claims,  that  this  is  no  new  factor ;  that  physiological 
selection  is  only  a  form  of  natural  selection.  This  objec- 
tion, it  seems  to  us,  is  little  more  than  a  play  upon 
words.  It  certainly  is  selection,  and  by  a  natural  pro- 
cess, and  therefore  in  some  sense  a  natural  selection,  but 
not  in  the  sense  of  Darwin.  It  is  not  a  selection  of  indi- 
viduals fittest  to  survive  ;  for  cross-fertile  individuals  are 
as  fit  to  survive  as  individuals,  though  not  as  species,  as 
are  cross-sterile.  Natural  selection  is  intent  only  on  pre- 
serving the  best  individuals  ;  physiological  selection  on 
preserving  the  kind.  Natural  selection  continues  the 
direction  of  progress  unchanged ;  physiological  makes 
new  directions. 

It  will  be  observed  that  Darwin  and  his  followers 
take  divergent  variations  of  offspring  simply  as  a  known 
fact,  upon  which  natural  selection  operates  to  produce 
progressive  modification.  And,  as  the  cause  of  variation 
in  offspring  is  wholly  unknown,  such  variations  are  often 
spoken  of  as  fortuitous.  But,  of  course,  it  is  well  under- 
stood that  nothing  in  Nature  is  really  fortuitous.     They 

may,  however,  for  all  jourposes  of  natural  selection  be 
5 


80    EVIDENCES  OF  THE  TRUTH  OF  EVOLUTION. 

thus  regarded  until  we  know  their  cause.  It  is  evident, 
then,  that  if  we,  with  Darwin,  take  natural  selection  as 
the  most  important  known  factor,  the  really  most  impor- 
tant cause  of  evolution  is  the  cause  of  varieties.  This  is 
the  unhnown  fundamental  factor.  As  Darwin  reduced 
Agassiz's  three  formal  laws  of  succession  to  more  general 
laws  of  life,  and  thus  made  one  important  step  in  the 
advance  of  biological  science,  so  he  who  shall  explain  the 
cause  of  divergent  variation  will  make  another  important 
step  by  reducing  the  phenomena  to  still  more  general 
and  fundamental  laws  of  life. 

In  conclusion,  let  me  again  impress  upon  the  reader 
that  all  the  doubt  and  discussion,  above  described,  as  to 
the  factors  of  evolution,  is  entirely  aside  from  the  truth 
of  evolution  itself,  concerning  which  there  is  no  differ- 
ence of  opinion  among  thinkers. 

Haying  now  prepared  the  mind  of  the  reader,  by  stat- 
ing briefly  what  it  is  we  wish  to  prove,  we  x)roceed  to 
give  some  of  the  most  im^Dortant  of  these  proofs. 


•    CHAPTER  III. 

SPECIAL   PROOFS,    TAKEN    FROil  THE    GEXEKAL   LAWS   OF 

AKIMAL   STRUCTURE,    OR   FROM   COMPARISON"   11^ 

THE   TAXONOMIC    SERIES. 

General  Pri7ici2jles. 

Analogy  and  Homology. — In  biology  those  organs  or 
parts  in  different  animals  are  said  to  be  analogous  which, 
however  different  their  origin,  have  a  general  similarity 
of  form  and  especially  of  function.;  while  those  are  called 
homologous  which,  however  different  their  general  ap- 
pearance, and  however  different  their  function,  yet  may, 
by  close  examination  and  extensive  comparison,  be  shown 
to  be  modifications  of  one  another — to  be,  in  fact,  origi- 
nally the  same  part  modified  for  different  purposes.  In 
the  former  the  parts  compared  look  and  behave  as  if  they 
were  the  same,  but  are  not ;  in  the  latter  they  look  and 
behave  entirely  differently,  but  are,  in  fact,  the  same 
part  in  disguise. 

We  can  best  make  this  plain  by  examples.  The  wing 
of  a  bird  and  the  wing  of  a  butterfly  are  analogous  or- 
gans. They  have  the  same  function — i.  e.,  flying;  and 
this  function  necessitates  the  same  general  form  of  a  flat 


82     EVIDENCES   OF  THE   TEUTH   OF  EVOLUTION. 

plane.  But  they  are  not  at  all  homologous  ;  they  are  not 
at  all  the  same  organ  or  part.  They  certainly  have  never 
been  formed  one  out  of  the  other  by  modification.  But 
the  wing  of  a  bird,  the  fore-paw  of  a  reptile  or  mammal, 
the  wing  of  a  bat,  and  the  arm  and  hand  of  a  man, 
though  so  different  in  form  and  function,  are  homologous 
parts.  On  close  examination  they  are  found  to  have  the 
same  general  structure,  to  be  composed  of  essentially  the 
same  pieces,  although  they  are  so  greatly  modified  in  or- 
der to  adapt  them  to  different  functions,  that  the  general 
or  superficial  resemblance  is  now  lost.  Their  structure  is 
precisely  such  as  it  would  be  if  they  had  all  originated 
from  some  archetypal  fore-limb  by  modifications  in  dif- 
ferent directions  of  its  several  parts.  By  extensive  com- 
parison in  the  taxonomic  and  ontogenic  series,  all  the 
intermediate  gradations  between  these  extreme  modifica- 
tions may  be  i:)iclved  up. 

Another  example.  The  lungs  of  a  mammal  and  the 
gills  of  a  fish  are  analogous  organs,  since  they  have  the 
same  function  of  aeration  of  the  blood.  But  they  are 
not  at  all  homologous  :  they  are  not  built  on  the  same 
plan  ;  by  no  effort  of  the  mind  can  we  imagine  that  the 
former  could  have  come  out  of  the  latter  by  modifica- 
tion. On  the  contrary,  we  have  positive  proof  that  it 
did  not  so  come.  But  there  is  an  organ  in  the  fish  which 
is  homologous  with  the  mammalian  lung,  viz.,  the  air- 
bladder,  or  swim-bladder.  We  know  it — 1.  Because  we 
can  trace  in  the  taxonomic  series  all  the  gradations  from 
the  one  to  the  other.     In  most  fishes  the  air-bladder  is 


SPECIAL  PEOOFS.  83 

wholly  cut  off  from  the  gullet,  and  only  very  feebly  sup- 
plied with  blood.  It  is  used  and  can  be  used  only  for 
flotation.  In  others,  as  the  gar-pike,  the  swim-bladder 
is  quite  yascular  and  opens  by  a  tube  into  the  throat. 
Through  this  optening  air  is  gulped  down  from  time  to 
time  into  the  bladder,  and  again  from  time  to  time  ex- 
pelled. In  other  words,  this  fish  supplements  its  gill- 
breathing  by  an  imperfect  lung-breathing.  We  have  here 
the  beginning  of  a  lung.  In  still  other  fishes,  viz.,  the 
Dipnoi  {lepidosireii  and  ceratodus,  Fig.  2),  the  air-blad- 


FiG.  2. — Lepidosiren. 

der  becomes  a  more  perfect  lung — i.  e.,  a  very  vascular 
sacculated  sac  ;  and  there  is  not  only  an  opening  into 
the  throat,  but  also  from  the  throat  to  the  snout.  In 
other  words,  we  have  for  the  first  time  nostrils.  These 
fishes  completely  combine  gill-breathing  w^ith  lung- 
breathing.  The  step  from  these  to  the  lowest  am- 
i^hibian  reptiles  is  so  small,  that  some  have  classed  the 
lepidosiren  among  amphibians  instead  of  fishes.  The 
siredon  or  axolotl  of  Kew  Mexico,  the  nee  turns  or  meno- 
branchus  of  our  Northern  lakes,  and  the  siren  of  our 
Southern  swamps,  have  both  gills  and  lungs,  and  breathe 
both  air  and  water ;  but  the  lung  is  very  imperfect,  beings 
only  a  sacculated  sac,  like  the  air-bladder  of  the  cerato- 


84    EVIDENCES   OF  THE  TRUTH  OF  EYOLUTIOK 

dus  and  le23idosiren.  ^No  one  doubts  that  the  air-breath- 
ing organ  of  an  amphibian  is  a  true  lung ;  yet  we  have 
traced  all  the  gradations  between  it  and  the  air-bladder 
of  a  fish.  We  conclude,  therefore,  that  if  there  be  any 
such  thing  as  transmutation  of  organic  forms,  the  lung 
of  higher  animals  must  have  been  formed  by  the  process 
aboYe  described.* 

But  we  know  it  still  more  certainly— 2.  Because  we 
can  trace  the  change  from  the  one  to  the  other  in  the  on- 
togenic  series.  In  the  life-history  of  the  individual  we 
can  actually  see  the  one  thing  change  into  the  other.  The 
frog,  as  is  well  known,  w^ien  first  hatched,  is  a  tadpole. 
It  has  no  legs,  but  locomotes  by  means  of  a  yertically- 
expanded  taih  It  has  no  lungs,  but  breathes  water  in- 
stead of  air,  by  means  of  gills.  It  is  in  all  respects, 
therefore,  a  fish,  and  would  be  classed  as  such  if  it  re- 
mained in  this  condition.  But  it  does  not ;  it  gradually 
loses  its  tail  and  gills,  and  acquires  legs  and  lungs,  and 
breathes  air  only.  JSTow  in  this  change  whence  came  the 
lungs  ?  From  the  gills  by  modification  ?  K'o  ;  but 
from  an  organ  similar  in  character  and  position  to  the 
air-bladder  of  a  ceratodus,  or  a  lepidosiren.  This  organ 
has  gradually  developed  into  a  Inng.  The  steps  of  the 
change  are  briefly  as  follow  :  First,  the  breathing  is 
wholly  water-breathing  by  gills.  Next,  by  the  develop- 
ment of  this  other  organ,  it  is  partly  water-breathing  by 

*  While  all  comparative  anatomists  agree  that  the  lung  is  a  diver- 
ticulum from  the  oesophagus,  like  the  air-bladder  of  the  gar-fish,  some 
think  that  it  is  a  different  diverticulum,  which  is  seen  first  in  the  dipnoi. 


SPECIAL  PROOFS.  85 

gills,  and  partly  air-breathing  by  lungs.  Lastly,  the  gills 
gradually  dry  up,  and  the  lungs  develop  more  and  more, 
until  the  breathing  is  wholly  by  lungs. 

We  have  dwelt  somewhat  upon  this  example,  because 
it  is  an  excellent  example  of  what  we  mean  by  homology, 
and  also  because  we  will  have  occasion  to  use  it  again. 
But  so  important,  for  all  that  follows  in  this  part,  is  a 
clear  idea  on  the  subject  of  homology,  that  it  will  be  best 
to  familiarize  the  mind  of  the  reader  with  it  by  means 
of  a  few  examples  drawn  from  plants. 

A  potato  is  analogous  to  a  root — a  tuberous  root  like 
that  of  a  dahlia  or  a  sweet-potato — but  is  not  at  all  ho- 
mologous with  these.  On  the  contrary,  it  is  homologous 
with  a  stem.  It  is  essentially  an  underground,  leafless 
branch,  which  has  thickened  enormously  at  the  point  by 
accumulation  of  starch.  The  evidence  of  this  is  found 
in  the  fact  that  it  has  rudimentary  leaves  (scales)  ar- 
ranged in  regular  spiral  order  of  phylotaxis,  each  with 
its  axillary  bud  (eyes).  It  is  still  more  clearly  shown  by 
the  fact  that  buds  above-ground  which,  if  let  alone, 
would  form  leafy  branches,  may  be  made  to  become  tu- 
bers by  covering  them  with  earth  or  dead  leaves,  and 
thus  excluding  the  light ;  and,  conversely,  underground 
buds  which,  if  let  alone,  would  form  tubers,  may  be 
made  to  grow  into  leafy  branches  by  exposing  them  to 
the  light. 

Take  another  example  :  The  broad,  flat,  elliptical, 
green  masses  so  characteristic  of  the  cactus  family,  and 
usually  called  their  leaves,  are  indeed  analogous  to  leaves 


86    EyiDE:N"CES   OF  THE   TRUTH   OF  EYOLUTIOX. 

in  color,  form,  and  function ;  for  they  are  green  and 
flat,  and  assimilate  carbonic  acid  and  water  (CO^  and 
H^O)  like  leayes.  But  they  are  not,  in  truth,  leaves, 
but  modified  stems,  for  they  have  the  essential  structure 
of  stems,  with  their  pith,  wood,  medullary  raj^s,  and 
bark,  and  may  be  traced  through  all  gradations  into 
the  ordinary  cylindrical  form  of  stems.  "Where  are  their 
leaves,  then?  Their  spines  are  their  abortive  leaves. 
These  are  arranged  spirally  like  leaves,  and  bear  buds 
in  their  axils  like  leaves.  They  are,  in  truth,  leaves, 
modified  to  perform  the  function  of  defensive  armor ; 
while  their  function  has  been  delegated  to  the  stem 
flattened  for  this  pur23ose. 

One  more  examj^le  :  The  acacias,  of  which  there  are 
fifteen  to  twenty  species  in  California,  introduced  from 
Australia,  form  two  grouj^s  having  extremely  different 
styles  of  leaves.  "We  will  call  them  the  feather-leaved 
and  the  simple-leaved  acacias.  In  the  former,  the  leaves 
are  very  finely  bipinnate,  and  the  general  asj)ect  of  the 
foliage  is  extremely  feathery  and  graceful.  In  the  latter 
the  leaves  are  simple,  ovate,  and,  curiously  enough,  set 
on  edge ;  and  the  general  aspect  of  the  tree  is  therefore 
rather  stiff.  It  seems  at  first  incredible  that  leaves  so 
different  and  asj)ects  so  diverse  should  belong  to  plants 
of  the  same  genus.  But  a  little  close  examination  shows 
that,  as  usual,  the  botanists  are  right  and  the  popular 
judgment  wrong.  The  plumose-leaf  is  the  normal  leaf- 
form  for  this  genus.  The  simple  leaf  is  not  only  abnor- 
mal, but  in  a  homological  sense  is  not  a  leaf  at  all— i.  e.. 


SPECIAL  PEOOFS. 


87 


it  does  not  correspond  to  the  part  called  the  hlade  in 
ordinary  simple  leaves  of  other  trees.  In  the  seedling  of 
the  simple-leaved  acacias,  and  sometimes  for  a  consider- 
able time  in  the  young  tree,  the  leaves  are  all  plumose. 
As  the  tree  matures  it  gradually  changes  its  dress  and 
puts  on  its  toga  virilis.     The  gradual  change  from  the 


Fig.  3. — A  branch  of  young  acacia,  showing  change  from  one  form  of 
leaf  to  the  other ;  a,  6,  c,  (7,  successive  stages  of  change  ;  l^  s,  leaf 
stalk  which  gradually  changes  into  the  blade  in  c,  </,  and  e. 

one  form  to  the  other  may  easily  be  traced  in  the  same 
tree,  and  even  often  in  the  same  branch  (Fig.  3).     The 


88    EVIDENCES   OF   THE  TRUTH   OF  EVOLUTION. 

steps  of  the  change  {a,  h,  c,  and  d)  are  shown  in  the  fol- 
lowing figure,  drawn  from  nature.  It  is  seen,  by  bare  in- 
spection of  the  figure,  that  the  so-called  leaf,  d,  of  the 
simple-leayed  acacias,  is  really  the  yertically-expanded 
leaf-stalk,  I,  s,  the  true  leaf  or  blade  being  wholly  aborted. 
The  whole  structure  of  this  so-called  leaf  is  different 
from  that  of  a  true  blade.  Por  example,  its  style  of  rib- 
bing is  parallel,  its  position  is  edgewise  to  the  sky,  its 
palisade  cells  are  on  both  sides  alike,  etc.  To  empha- 
size this  difference,  botanists  call  such  an  apparent  leaf  a 
pJiyUodium,  or  phyllode. 

After  these  illustrations  we  now  repeat  the  defini- 
tions in  different  words.  Analogy  has  reference  to 
general  resemblance  of  form  determined  by  similarity 
of  function ,  however  different  the  origins  of  the  parts 
compared  may  be.  Homology  has  reference  to  com- 
munity of  origin,  however  obscured  to  the  superficial 
observer  such  common  origin  may  be  by  modifications 
necessary  to  adapt  to  different  functions.  Observe, 
then,  there  are  two  ideas  here  which  must  be  kept 
distinct.  One  is  common  origin,  always  shown  by 
deep-lying,  essential  identity  of  structure ;  the  other 
is  adaptive  modification  for  function.  Organs  of  the 
most  diverse  origin  may  resemble  by  adaptive  modifi- 
cation for  the  same  function.  This  is  analogy.  Or- 
gans of  the  same  origin  may  assume  very  different 
appearance  by  adaptive  modifications  for  different  func- 
tions. This  is  homology.  In  the  latter  case,  which  is 
the  one  that  concerns  us,  a  profound  study  of  essential 


SPECIAL  PPvOOFS.  89 

structure  and  structural  relations  to  other  parts,  and 
especially  extensive  comparison  in  the  taxonomic  and 
ontogenic  series,  will  usually  detect  the  homology,  or 
common  origin,  in  spite  of  the  obscurations  produced  by 
adaptive  modifications.  It  is  seen,  also,  that  analogy  is 
a  superficial  resemblance,  easily  detected  by  the  popular 
eye,  and  therefore  embodied  in  popular  language  ;  while 
homology  is  a  deep-seated  and  essential  resemblance, 
detected  often  only  by  profound  study  and  extensive 
comparison.  !N'ow,  one  of  the  strongest  proofs  of  the 
truth  of  evolution  is  taken  from  the  homologies  of  ani- 
mal structure.  Common  origin  completely  explains 
homology.  Every  other  explanation  is  transcendental, 
and  therefore  unscientific. 

Primary  Divisions  of  the  Animal  Kingdom.— Now, 
the  animal  kingdom  consists  of  several  primary  divisions, 
called  sub-kingdoms  or  departments.  The  animals  in 
these  groups  differ  so  essentially  from  one  another  in  their 
plan  of  structure,  that  it  is  difiicult,  if  not  impossible,  to 
trace  any  structural  relation  between  them — to  imagine 
how  the  members  of  one  could  have  been  derived  from 
those  of  another — or  conceive  the  common  stem  from 
which  they  all  separated.  In  other  words,  it  is  impos- 
sible, in  the  present  state  of  knowledge,  to  trace  ho- 
mology with  any  certainty  from  one  group  to  an- 
other. But  within  the  limits  of  each  primary  group 
the  homology  is  easy.  Some  naturalists — Agassiz  and 
Cuvier — have  made  four  or  five  of  these  primary  groups. 
Some — Huxlev — have  made  eifjfht.     Some  make  nine  or 


90    EVIDENCES   OF  THE  TRUTH   OF   EVOLUTION. 

ten.*  We  wiH  not  trouble  ourselves  to  settle  this  ques- 
tion ;  for  all  agree  to  make  vertehrata  and  articulata  or 
arthropoda  two  of  them,  and  all  our  illustrations  will  be 
drawn  from  these.  Other  groups  are  too  unfamiliar  to 
the  general  reader  to  serve  our  purpose. 

Now,  as  already  stated,  homology  can  not  be  traced 
with  any  certainty  between  the  primary  groujDS,  but 
within  the  limits  of  each  group  it  may  be  traced  with 
ease  and  beauty.  Analogy,  however,  being  connected 
with  function,  and  function  being  universal,  can  be 
traced  throughout  the  animal  kingdom.  While,  there- 
fore, it  is  probable,  hay,  almost  certain,  that  all  animals 
have  had  a  common  origin,  we  can  not  yet  trace  these 
great  departments  by  homology  to  that  common  origin. 
But  the  common  origin  of  each  department  is  quite  clear. 
For  example,  the  structure  of  all  vertebrate  animals  is 
precisely  such  as  would  be  the  case  if  aU  came  from  one 
primal  vertebrate,  variously  modified  to  adaj^t  to  vari- 
ous modes  of  life.  Also,  the  structure  of  all  arthropods 
is  precisely  such  as  would  be  if  all  came  from  one  primal 
arthropod,  which,  from  generation  to  generation,  be- 
came gradually  modified  in  different  directions,  in  order 
to  adapt  itself  to  various  modes  of  life.     But  between 

*  Undoubtedly  the  true  principle  on  which  primary  groups  ought  to 
be  made  is,  identity  of  general  plan  of  siructure,  or  traceahleness  of  ho- 
mology throughout.  For  these  groups  are  the  great  primary  branches  of 
the  tree  of  life,  and  classification  ought  to  represent  degrees  of  genetic 
relationship.  This  was  Agassiz's  principle,  although  he  did  not  admit  the 
genetic  relation.  This  principle  has  been,  it  seems  to  us,  too  much  neg- 
lected by  later  systematists. 


SPECIAL   PROOFS.  91 

arthropods  and  vertebrates  we  can  not  yet  clearly  see  a 
common  origin,  although  there  doubtless  was  such. 

These  great  departments  may,  therefore,  be  compared 
to  natural  styles  of  animal  architecture.  As  there  are 
various  styles  of  human  architecture — Oriental,  Egyp- 
tian, Greek,  Gothic — each  of  which  may  be  variously 
modified  to  adapt  it  to  all  the  different  purposes  for 
which  buildings  are  made,  without  destroying,  though 
perhaps  obscuring,  the  integrity  of  the  style  ;  so  the  dif- 
ferent primary  groups  or  departments  may  be  regarded 
as  different  styles  of  animal  structure,  each  of  which 
may  be  and  has  been  modified  in  many  ways  to  adapt  it 
to  various  habits  and  modes  of  life,  obscuring  but  not 
destroying  the  general  style.  Or  they  may  be  compared 
to  natural  macliines.  As  a  steam-engine,  by  modifica- 
tion, may  be  adapted  to  many  kinds  of  purposes,  obscur- 
ing, perhaps,  but  not  destroying  the  essential  identity  of 
structure  ;  even  so  the  vertebrate  machine  by  modifica- 
tion may  be,  and  has  been,  adapted  to  many  kinds  of 
purposes,  and  thus  become  a  swimming-machine,  a 
crawling-machine,  a  flying-machine,  a  running-  and  leap- 
ing-machine,  without  destroying,  although  obscuring, 
the  essential  identity  of  structure.  As  in  architecture, 
aesthetic  principles  of  form  may  be  traced  through  each 
style,  but  not  from  style  to  style,  while  the  mechanical 
principles  of  construction  run  through  all  alike  ;  so 
also  in  animal  architecture,  the  laws  of  form  and  styles 
of  structure  are  traceable  with  ease  only  within  the 
limits  of  each  primary  group,  while  the  laws  of  function 


02    EVIDENCES   OF  THE  TRUTH  OF  EYOLUTION". 

are  traceable  througli  all  groups  alike.  Or,  again,  and 
finally  :  Each  of  these  departments  may  be  compared  to 
a  tree,  with  branches,  twigs,  and  spray,  all  obviously 
coming  from  one  common  stem,  but  each  stem  seems 
separate.  They  are,  indeed,  probably,  themselves  only 
great  branches  of  one  common  trunk,  but  their  connec- 
tion is  too  remote  and  obscure  to  be  made  out  clearly  by 
means  of  homology.  Other  evidences,  however,  drawn 
from  other  sources,  as  we  shall  see  hereafter,  are  not 
wholly  wanting. 


CHAPTER  IV. 

PROOFS  FROM   HOMOLOGIES   OF  THE   VERTEBRATE 

SKELETOisT. 

The  proposition  to  be  established  here  is,  that  all  yer- 
tebrates  haye  not  only  a  common  general  plan  of  struct- 
ure, but  an  essential  identity  eyen  in  detail,  although 
this  identity  is  obscured  by  adaptiye  modifications.  We 
will  try  to  show  first  a  common  general  'plan,  and  then, 
taking  parts  most  familiar  to  the  general  reader,  will 
show  essential  identity  eyen  in  detail. 

Commoii  General  Plan. — 1.  All  vertebrate  animals,  and 
none  other,  have  an  i7iternal  jointed  skeleton  worked  by 
muscles  on  the  outside.  As  we  shall  see  hereafter,  the 
relation  of  skeleton  and  muscle  in  arthropods  is  exactly 
the  reverse. 

2.  In  all  vertebrates,  and  in  none  other,  the  axis  of 
this  skeleton  is  a  jointed  backbone  (vertebral  column) 
inclosing  and  protecting  the  nervous  centers  (cerebro- 
spinal axis).  These,  therefore,  may  well  be  called  back- 
boned animals. 

3.  All  vertebrates,  and  none  other,  have  a  number  of 
their  anterior  vertebral  joints  enlarged  and  consolidated 


94    EVIDENCES   OF   THE  TRUTH   OF  EVOLUTION. 


into  a  box  to  form  the  skull,  in  order  to  inclose  and  pro- 
tect a  similar  enlargement  of  the  nervous  center,  yiz.,  the 
brain  ;  and  also  usually,  but  not  always,  a  number  of  pos- 
terior joints,  enlarged  and  consolidated  to  form  the  pel- 
vis, to  serve  as  a  firm  support  to  the  hind-limbs. 

4.  All  vertebrates,  and  none  other,  have  two  cavities, 
inclosed  and  protected  by  the  skeleton,  viz.,  the  neural 
cavity  above,  and  the  visceral  or  body  cavity  below,  the 
vertebral  column  ;  so  that  a  cross-section  of  the  body  is 
diagrammatically  represented  by  Fig.  4. 

5.  All  vertebrates,  with  few  ex- 
ceptions, and  no  other  animals,  have 
^  two  and  only  two  pair  of  limbs. 
The  exceptions  are  of  two  kinds, 
viz.  :  a,  some  lowest  fishes,  amphi- 
oxus  and  lampre3^s,  which  probably 
represent  the  vertebrate  condition 
before  limbs  were  acquired  ;  and  Z>, 
degenerate  forms  like  snakes  and 
some  lizards,  which  have  lost  their 
limbs  by  disuse. 

So  much  concerns  the  general 
plan  of  skeletal  structures,  and  is 
strons^ly  suo^orestive  of — in   fact,   is 

cavity  ;    r,    visceral      ^  &  .;         &&  ^  ?     ^ 

cavity ;  c,  centrum  of     inexplicable  without — common  ori- 

gm.       But     much    more     remains 

which  is  not  only  suggestive,  but  demonstrative  of  such 

origin.     By  extensive  comparison  in  the  taxonomic  and 

ontogenic   series,   the  whole  vertebrate  structure  in  all 


Fig.  4. — Diagram  cross- 
section  tlirou2;h  the 
body  of  a  vertebrate, 
showing  the  relation 
of  skeleton  to  the 
cavities,     n.    neutral 


PROOFS  FROM  HOMOLOGIES.  95 

its  details  in  different  animals  may  be  shown  to  be  modi- 
fications one  of  another.  Sometimes  a  piece  is  enlarged, 
sometimes  diminished,  or  eyen  becomes  obsolete  ;  some- 
times several  pieces  are  consolidated  into  one  ;  but,  in  spite 
of  all  these  obscurations,  corresponding  parts  may  usually 
be  made  out.     This  is  the  main  subject  of  this  chapter. 

Special  Homology  of  Vertebrate  Limbs.— It  would 
lead  us  much  too  far  into  unfamiliar  technicalities  to 
take  up  the  whole  skeleton.  We  select  the  limbs,  both 
because  their  general  structure  is  more  familiar,  and  be- 
cause in  them  the  two  fundamental  ideas  of  essential 
identity  and  of  adaptive  modification  are  both  admirably 
illustrated.  The  reason  of  this  is,  that  it  is  by  the  limbs 
that  the  organism  chiefly  reacts  on  the  environment,  and 
is  modified  by  it. 

Fore-limbs. — In  the  accompanying  figures  (Figs.  5- 
18)  we  have  represented,  side  by  side,  the  fore-limbs  of 
many  vertebrates,  taken  from  all  the  classes — mammals, 
birds,  reptiles,  and  fishes.  For  convenience  of  compari- 
son, the  corresponding  parts  are  similarly  lettered  in  all. 
Also,  in  order  to  identify  easily  certain  important  corre- 
sponding segments,  we  have  drawn  through  them  a  con- 
tinuous dotted  line.  In  man,  nearly  all  the  parts  are 
present,  and  his  limbs,  therefore,  may  be  taken  as  a  term 
of  comparison ;  for  man's  structure,  except  his  brain,  is 
far  less  modified  than  that  of  many  animals. 

Note,  then,  the  following  points  :  1.  The  collar-bone 
(clavicle)  is  associated  with  wide  separation  of  the  shoul- 
ders, and  the  free  use  of  the  fore-limb  for  prehension  or 


90    EVIDENCES   OF   THE   TFwUTH   OF  EYOLUTIOK 

for  flight,  but  is  gradually  lost  in  proportion  as  the  fore- 
limb  is  brought   nearer  together  and  used  for  suj^port. 


because  it  is  no  longer  wanted.  I  say  gradually,  for  all 
the  steps  of  the  passing  away  may  be  found.  The  use- 
less rudimentary  condition  is  not  uncommon. 


PROOFS   FROM  HOMOLOGIES. 


97 


2.  The  coracoid  (c),  it  is  seen,  is  a  small,  beak-like 
process  of  the  blade-bone  (scapula)  in  man  and  mam- 
mals ;  but  in  birds  (Fig.  11)  and  reptiles  (Figs.  14,  18) 


•^cc^ 


Fig.  10.  Fig.  11.  Fig.  12.  Fig.  13. 

Figs.  10-13. — 10.  Fore-limb  of  bat.  11.  Bird.  12.  Archseopteryx.  13. 
Pterodactyl.  (Lettered  as  in  previous  figures  ;  grouped  from  various 
sources.) 

it  is  a  separate  bone  as  large  as  the  blade-bone  itself, 
jointed  with  the  latter  at  the  shoulder  and  with  the 
breast-bone  (sternum)  in  front,  thus  making  together  a 
strong  shoulder-girdle  for  the  attachment  of  the  fore- 
limb.  This  was  undoubtedly  the  condition  in  the  origi- 
nal or  earliest  walking  animal,  viz.,  reptiles.  It  was 
inherited  and  retained  by  birds,  because  necessary  for 
powerful  action  of  the  wings  in  flight.  In  mammals  it 
gradually  dwindled  and  became  united  with  the  blade- 
bone  as  a  process.     In  one  mammal,  the  lowest  and  most 


98    EVIDENCES   OF   THE   TRUTH   OF  EVOLUTIOK 

reptilian  living — the  ornithorliynclius — tlie  coracoid  is 
much  like  that  of  re|)tiles — a  large,  flat  bone,  separated 
from   the   blade-bone   and   articulated  with   the   breast- 


FiG.  14.  Fig.  15.  Fiu.  16.        Fig.  17. 

Figs.  14-17.— 14.  Fore-limb  of  turtle.     15.  Mole.    16.  Whale.    17.  Fish. 

bone.  It  is  a  significant  fact  that,  in  the  mammalian 
embryo,  it  is  first  developed  as  a  separate  bone  and 
afterward  united  with  the  scapula. 

3.  In  man,  monkeys,  bears,  and  some  other  mam- 
mals, the  limb  is  fairly  free  from  the  body  and  the  el- 
bow half-way  down  the  limb  ;  while  in  herbivores  (Figs. 
8,  9),  such  as  the  horse,  ox,  and  deer,  etc.,  the  elbow  is 
high  on  the  side  of  the  body,  and  the  limb  is  free  only 
from  the  elbow  downward.  Perhaps  in  these  cases  most 
observers  do  not  recognize  it  as  an  elbow  at  all.  All 
gradations  between  these  extremes  are  easily  traced. 
The  free  condition  of  the  limb  is  evidently  the  original 
one,  the  condition  in  herbivores  being  an  extreme  modi- 


PEOOFS   FROM  HOMOLOGIES. 


99 


fication  associated  with  another  modification  mentioned 
under  5. 

4.  In  man  and  in  many  mammals,  and  in  all  reptiles 
and  birds,  there  are  two  bones  in  the  forearm  (radius 
and  ulna).  In  the  more  spe- 
cialized forms  of  hoofed  animals 
(ungulates),  such  as  horse  and 
ruminants  (Figs.  8,  9),  there  is 
apparently  but  one.  Two  is  the 
normal  and  original  number ; 
but  one  of  them,  the  ulna,  has 
gradually  become  smaller  and 
smaller,  and  finally  is  reduced 
to  a  short  splint,  and  consoli- 
dated with  the  radius  as  a  pro- 
cess extending  backward  to  form 
the  j)oint  of  the  elbow.  In  the 
horse  family  every  step  of  this 
reduction  and  consolidation  may 
be  traced  in  the  course  of  its 
geological  history. 

5.  The  ivrist  of  many  mam- 
mals and  all  birds  differs  in 
structure  from  that  of  man, 
chiefiy  in  containing  a  smaller 
number  of  bones.  The  normal 
number,  as  in  man,  seems  to  be 
eight.  The  decrease  takes  place 
mainly  by  consolidation  of  two  or  more  into  one.     In  such 


100  EVIDENCES   OF  THE  TRUTH  OF  EVOLUTION. 

cases  usually  the  embryo  will  show  the  bones  still  separate, 
thus  revealing  the  ancestral  condition.  Again,  the  posi- 
tion of  the  wrist  is  noteworthy.  In  man,  monkeys,  the 
bear  family,  and  several  other  mammalian  families,  and 
in  all  reptiles,  the  hand  bends  forward  at  the  wrist,  so 
that  the  tread  is  on  the  w^hole  palm  (palmigrade).  But, 
in  all  the  most  specialized  mammals,  the  wrist  can  not 
bend  in  this  direction,  and  therefore  this  joint  can  not  be 
brought  to  the  ground.  The  tread  is  therefore  on  the 
toes  (digitigrade),  and  the  wrist  is  high  up  above  the 
ground.  In  the  horse  (Fig.  9),  the  ox,  and  many  other 
mammals,  for  example,  the  wrist  is  so  high  that  it  is 
not  usually  recognized  as  a  wrist,  and  is  often  called 
the  fore-hnee.  ISTow,  homologous  parts  ought  to  have 
the  same  scientific  name;  but  to  use  the  word  '^liand^^ 
in  the  case  of  lower  animals  might  produce  confusion 
and  misconception.  Therefore  it  has  been  agreed  among 
comparative  anatomists  to  use  instead  the  Latin  word 
^^7nanus"  for  all  that  corresponds,  in  any  animal,  to 
the  hand  of  man — i.  e.,  all  from  the  wrist  downward. 
The  manus  of  a  horse  is  about  fifteen  inches  long.  The 
manus  of  a  pterodactyl,  such  as  that  found  by  Marsh 
in  the  cretaceous  strata  of  the  West,  with  an  expanse 
of  wings  of  twenty-five  feet,  wa^  probably  not  less  than 
seven  or  eight  feet  long. 

6.  The  number  of  palm-bones  (metapodal)  and  toes 
deserves  special  notice.  In  fishes,  and  in  some  extinct 
swimming  reptiles,  these  are  or  were  very  numerous,  but 
in  the  earliest  land-aninials  they  became  five.     This  is 


PEOOFS  FEOM  HOMOLOGIES.  101 

the  number  now  in  nearly  all  reptiles,  and  in  all  the 
more  generalized  mammals.  It  may  be  called  the  normal 
number  for  a  walking  animal.  In  very  many  mammals, 
such,  for  example,  as  the  dog  family,  they  are  reduced  to 
four,  though  the  fifth  often  remains  as  a  useless,  rudi- 
mentary splint  and  dew-claw  (Fig.  6),  thus  showing  the 
process  of  dwindling  in  the  ancestry.  In  hoofed  ani- 
mals the  process  of  gradual  diminution  is  shown  even 
in  existing  forms,  and  still  better  in  extinct  forms. 
Confining  ourselves,  now,  only  to  existing  forms,  in  the 
elephant  there  are  five  palm-bones  and  toes,  and  in  the 
hippopotamus  there  are  four,  all  functional.  In  the  hog 
(Fig.  7)  there  are  still  four,  but  two  are  behind  the 
others  and  much  smaller,  and  do  not  touch  the  ground 
— are  not  functional  unless  in  soft  ground.  In  the  cow, 
deer,  etc.,  the  palm-bones  are  reduced  to  two,  and  these 
are  consolidated  into  07ie  (canon-bone),  and  the  toes  are 
reduced  to  two  eflScient  and  two  useless  rudiments.  In 
the  sheep  and  the  goat  (Fig.  8)  these  useless  rudiments 
are  dropped,  and  there  are  two  only.  Finally,  in  the 
horse  (Fig.  9),  the  toes  are  reduced  to  one,  although  the 
palm-bones  are  still  three,  two  of  them,  however,  being 
reduced  to  rudimentary  splints. 

How  is  it  with  birds  ?  Have  these  also  palm-bones 
and  fingers  ?  Yes,  in  birds  (Fig.  11)  there  are  three 
palm-bones  and  three  fingers  (the  fourth  and  fifth  being 
wanting)  ;  one  of  them — the  thumb — is  free,  and  some- 
times carries  a  claw.  In  the  earliest  known  and  most 
reptilian  bird,  the  archasopteryx  (Fig.  12),  all  the  three 


102  EVIDENCES   OF  THE  TRUTH  OF  EVOLUTION. 


fingers  are  free,  have  the  full  number  of  joints,  and  all 
of  them  carry  claws.     In  the  embryo  of  living  birds  the 

fingers  are  all  free,  as 
in  the  archseoj^teryx. 

7.  Observe,  finally, 
as  an  admirable- illus- 
tration of  different 
adaptative  modifica- 
tions for  the  same  pur- 
pose —  flight  —  the 
structure  of  the  manus 
of  flying  animals.  In 
the  bat  (Fig.  10),  the 
flat  flying  -  plane  is 
made  by  enormous 
elongation  of  the  palm- 
bones  and  finger-bones, 
their  wide  separation 
and  the  stretching  of 
a  thin  membrane  be- 
tween them.  In  the 
pterosaurs,  or  extinct 
flying  reptiles  (Fig. 
13),  one  finger  only  is 
greatly  eularged  and 
elongated,  and  the  flyiug-membrane  is  stretched  between 
it  and  the  hind-leg  (Fig.  19),  while  the  other  three  fingers 
are  free  and  provided  with  claws.  If  it  be  asked  which 
finger  is  it  that  is  so  greatly  enlarged  in  this  animal, 


PROOFS   FROM  HOMOLOGIES.  103 

we  answer,  it  is  the  little  finger.  In  birds,  on  the  con- 
trary, the  manus  is  consolidated  to  the  last  dec'ree,  to 
form  a  strong  basis  for  attachments  for  the  quills  which 
form  the  flying-plane,  and  which  are  themselves  extreme 
modiflcations  of  the  scales  of  reptiles.  But  throughout 
all  these  extreme  modifications  the  same  essential  struct- 
ure is  detectable. 

It  is  perhaps  unnecessary  to  dwell  upon  the  still 
greater  modifications  of  limbs  for  swimming,  as  in  the 
whale  (Fig.  16),  the  ichthyosaur,  mosasaur  (Fig.  18), 
and  the  fish  (Fig.  17).  A  careful  inspection  of  the 
figures,  after  what  we  have  said,  will  be  sufficient  to 
explain  them.  In  the  fish  alone  the  upper  segments  of 
the  limb,  viz.,  shoulder-girdle  and  humerus,  are  want- 
ing, not  being  yet  introduced,  and  the  manus  is  not 
yet  differentiated  into  palm-bones  and  fingers,  and  the 
fingers  are  indefinitely  multiplied.  All  these  characters 
are  indications  of  low  position  in  the  scale  of  evolu- 
tion. The  earliest  vertebrates  were  fishes.  Limbs  were 
not  yet  completely  formed.  In  embryos  of  higher  ani- 
mals, also,  the  outer  segments  are  first  formed. 

Hind-Limbs. — Figs.  20  to  24  represent,  in  a  similar 
way,  the  hind-limbs  of  several  animals — in  this  case  all 
mammals.  As  before,  corresponding  parts  are  similarly 
lettered,  and  a  dotted  line  is  carried  through  certain 
prominent  parts,  especially  the  knee,  heel,  instep,  and 
toes.  By  careful  inspection  the  figures  explain  them- 
selves. Nevertheless,  it  will  be  well  to  draw  special  at- 
tention to  several  of  the  more  important  points : 


104    EVIDENCES   OF   THE   TEUTH   OF   EVOLUTION". 

1.  See,  then,  the  j)ositioii  of  the  knee.  The  thigh- 
bone in  man,  monkeys,  bears,  and  several  other  families 
of  mammals,  and  all  reptiles,  is  free  from  the  body,  and 


PROOFS  FROM  HOMOLOGIES.  105 

the  knee  is  far  removed  and  half-way  down  the  limb 
(Figs.  20,  21).  This  is  undoubtedly  the  original  and 
normal  condition  of  land-animals.  But  in  all  the  more 
highly  s^Decialized  and  swifter  animals  the  knee  is  brought 
nearer  and  nearer  to  the  body,  until,  in  the  swiftest  of 
all,  such  as  the  ruminants  and  the  horse  (Figs.  23,  24), 
it  is  high  up  on  the  side  of  the  body,  in  the  middle  of 
what  is  usually  called  the  thigh  but  which  really  includes 
the  thigh  and  the  upper  part  of  the  lower  leg  or  shank, 

2.  See,  again,  the  position  of  the  heel.  In  man, 
monkey,  bear,  and  many  other  mammals,  and  all  living 
reptiles,  the  heel  is  on  the  ground,  the  tread  is  on  the 
whole  foot,  plantigrade  ;  while  in  all  the  more  special- 
ized and  agile  animals,  and  especially  in  the  swiftest  of 
all,  such  as  the  horse,  the  deer,  etc.,  the  heel  is  high  in 
the  air,  and  the  tread  is  digitigrade. 

3.  Observe,  again  :  there  are  two  degrees  of  digiti- 
gradeness.  The  one  we  find  in  carnivorous  or  clawed 
digitigrades,  the  other  in  herbivores  or  hoofed  digiti- 
grades.  In  the  one  the  tread  is  on  the  whole  length  of 
the  toes  to  the  balls,  as  in  man  when  he  tip-toes;  in 
the  other  the  tread  is  on  the  tip  of  the  last  joint  alone. 
All  that  in  any  animal  corresponds  to  the  foot  of  a 
man — i.  e.,  from  the  hamstring  and  heel  downward — 
is  called,  in  comparative  anatomy,  the  ^^ pes.^^  The  pes, 
or  foot  of  a  horse,  is  eighteen  inches  long.  It  is  easy 
to  see  what  spring  and  activity  this  mode  of  treading 
gives  to  an  animal.  Think  how  helpless  a  horse  would 
be  if  he  trod  on  the  whole  foot,  heel  down  ! 


106    EVIDENCES   OF  THE   TRUTH   OF  EVOLUTION. 

4.  Observe,  again,  the  number  of  toes.  In  the  pro- 
cess of  specialization  there  is  a  tendency  for  these  to 
become  fewer  and  stronger.*  The  normal  number,  as 
already  seen,  is  five.  All  the  earliest  mammals,  and 
many  orders  of  mammals  still  living,  have  five ;  but  in 
the  most  specialized  orders,  such  as  the  ungulates  or 
hoofed  animals,  they  were  steadily  reduced  in  number  in 
the  course  of  evolution.  In  the  elephant  there  are  still 
five,  in  the  hippopotamus  there  are  four,  in  the  rhinoce- 
ros three,  in  the  goat  two,  in  the  horse  one.  Still  more 
the  order  of  the  dropping  is  regular.  If  an  animal 
have  but  four  toes,  it  is  usually  the  first,  or  great  toe, 
or   thumb,   that   is   wanting,   or   may   be    rudimentar}^ 

*  This  is  only  oue  example  under  a  general  law  which  it  may  be 
well  to  stop  a  moment  to  illustrate.  A  repetition  of  similar  parts  per- 
forming the  same  function  is  always  an  evidence  of  low  organization, 
and  as  we  rise  in  the  scale  of  organization  such  parts  usually  become 
fewer  and  more  efficient.  Thus,  to  give  one  example,  myriapods,  as  their 
name  indicates,  have  hundreds  of  locomotive  organs — lower  crustaceans 
perhaps  thirty  or  forty.  As  we  go  up,  they  are  reduced  to  fourteen  (tct- 
radecapods),  then  to  ten  (decapods),  then  in  spiders  to  eight,  in  insects 
to  six,  in  vertebrates  to  four,  and  in  man  to  two.  A  similar  reduction  in 
number,  but  increase  in  efficiency,  is  found  in  toes,  when  they  are  used  for 
support  and  locomotion  only.  In  man  we  find  the  normal  number  of  five 
(1),  because  his  hands  are  used  for  grasping  and  the  functions  of  the 
fingers  are  not  the  same ;  and  (2),  because  man's  development  was  almost 
wholly  hrainioard.  In  other  respects  his  structure  is  far  less  specialized 
than  most  other  mammals.  He  can  not  compete  with  carnivores  in 
strength  and  ferocity,  nor  with  herbivores  in  fleetness.  In  the  struggle 
for  life,  therefore,  there  was  nothing  left  for  him  but  increase  in  intelli- 
gence. Probably  four  is  the  smallest  number  of  locomotive  organs  con- 
sistent with  highest  efficiency.  In  retaining  but  two  legs  for  locomotion, 
man  has  lost  in  locomotive  efficiency,  but  by  the  sacrifice  he  liberates  two 
limbs  for  higher  functions. 


PROOFS  FROM  HOMOLOGIES.  107 

If,  as  in  the  rhinoceros,  there  are  only  three,  then  No. 
5,  or  little  toe,  is  also  wanting,  and  the  existing  toes 
are  Nos.  2,  3,  and  4.  If  an  animal  has  only  two  toes, 
as  the  goat,  these  are  Nos.  3  and  4;  and  if  only  one, 
as  the  horse,  it  is  the  third  or  middle  toe.  Or,  to  put 
it  more  definitely  :  hoofed  animals  are  divided  into  two 
groups,  even-toed  (artiodactyl)  and  odd-toed  (perisso- 
dactyl).  The  even-toed  may  have  four,  as  in  the  hip- 
popotamus ;  or  two,  as  in  the  goat.  The  odd-toed 
may  have  three,  as  in  the  rhinoceros ;  or  but  one,  as 
in  the  horse.  Now,  both  of  these  orders  came  by  dif- 
ferentiation, far  back  in  the  Eocene  Tertiary,  from  a 
five-toed  plantigrade  ancestor.  After  dropping  No.  1 
(thumb  or  great  toe)  it  is  not  yet  decided,  so  far  as  num- 
ber of  toes  is  concerned,  whether  the  resulting  four-toed 
animal  shall  become  artiodactyl  or  perissodactyl.  If  the 
former,  then  the  two  side-toes  (Nos.  2  and  5)  become 
shortened  up,  as  in  the  hog ;  then  rudimentary,  as  in  the 
ox  and  deer ;  and  finally  pass  away  entirely,  as  in  the 
goat.  If,  on  the  other  hand,  the  four-toed  animal  is  on 
the  line  of  perissodactyl  evolution,  it  becomes  first  a 
three-toed  animal  by  dropping  No.  5.  Now,  the  two  side- 
toes  (Nos.  2  and  4)  shorten  up  more  and  more,  and  the 
middle  toe  increases  in  size,  until  finally,  in  the  modern 
horse,  only  the  greatly  enlarged  middle  toe  (No.  3)  re- 
mains. We  look  with  wonder  and  admiration  at  the 
danseuse  pirouetting  on  the  point  of  one  toe.  The 
horse  is  performing  this  feat  all  the  time.  Yes,  the 
one  toe  of  a  horse  has  all  the  three  joints  like  ours. 


108    EVIDENCES   OF   THE   TRUTH   OF  EVOLUTION. 

The  coffin-bone  is  the   last  joint,   and    the  hoof   is  the 
naiL 

Genesis  of  the  Horse. — Every  step  of  this  process  on 
the  perissodactyl  line  may  be  traced  in  the  history  of 
the  genesis  of  the  horse.  The  beautiful  form  and  struct- 
ure of  this  animal  were  not  made  at  once,  but  by  a  slow 
process  of  integration  of  small  changes  from  generation 
to  generation,  and  from  epoch  to  epoch  of  the  earth's 
history.  The  horse  (as  in  fact  did  all  ungulates)  came 
from  a  five-toed  plantigrade  ancestor,  but  we  are  not 
able  to  trace  the  direct  line  of  genesis  quite  so  far.  The 
earliest  stage  that  we  can  trace  with  certainty,  in  this 
line  of  descent,  is  found  in  the  eohippus  of  Marsh.  This 
was  a  small  animal,  no  bigger  than  a  fox,  with  three  toes 
behind  and  four  serviceable  toes  in  front,  with  an  ad- 
ditional fifth  palm-bone  (splint),  and  perhaps  a  rudi- 
mentary fifth  toe  like  a  dew-claw.  This  was  in  early 
Eocene  times.  Then,  m  later  Eocene,  came  the  orohip- 
pus,  which  differs  from  the  last  chiefly  in  the  disappear- 
ance of  the  rudimentary  fifth  toe  and  splint.  (See  Fig. 
25.)  Next,  in  the  Miocene,  came  the  mesohippus  and 
miohippus.  These  were  larger  animals  (about  the  size  of 
a  sheep),  and  had  three  serviceable  toes  all  around ;  but 
in  the  former  the  rudiment  of  a  fourth  splint  in  the  fore- 
limb  yet  remained.  Then,  in  the  Miocene,  came  the  pro- 
tohippus  and  pliohippus.  These  were  still  larger  ani- 
mals, being  about  the  size  of  an  ass.  In  the  former  the  two 
side-toes  were  shortening  up  and  the  middle  toe  becom- 
ing larger.     In  the  latter  the  two  side-toes  have  become 


Equus :  Qua- 
ternary and 
Recent. 


Pliohippus  : 
Pliocene. 


Protohippus  ; 
Lower  Plio- 
cene. 


JJiohippus ; 
Miocene. 


Mesohippus : 
Lower  Mio- 
cene. 


Orohippus 
Eocene. 


PROOFS  FEOM  HOMOLOGIES. 

d 


Fig.  25. — Diagram  illustrating  gradual  changes  in  the  horse  family. 
Throughout  a  is  fore-foot ;  '6,  hinci-foot ;  c,  fore-arra  ;  d,  shank ;  e, 
molar  on  side-view  ;  /  and  y,  grinding  surface  of  upper  and  lower 
molars  (after  Marsh j. 


110    EVIDENCES   OF  THE   TRUTH   OF  EVOLUTION. 

splints.  Lastly,  only  in  the  Quaternary  conies  the  genus 
Equus,  or  true  horse.  The  size  of  the  animal  is  become 
greater,  the  middle  toe  stronger,  the  side-splints  smaller  ; 
but  in  the  side-splints  of  tlie  modern  horse  we  have  still 
remaining  the  evidence  of  its  three-toed  ancestor. 

Similar  gradual  changes  may  be  traced  in  the  two 
leg-bones,  which  have  gradually  consolidated  into  one  ; 
in  the  teeth,  which  have  become  progressively  longer  and 
more  complex  in  structure,  and  therefore  a  better  grind- 
er ;  in  the  position  of  the  heel  and  wrist,  which  have 
become  higher  above-ground  ;  in  the  general  form,  which 
has  become  more  graceful  and  agile  ;  and,  lastly,  in  the 
brain,  which  has  become  progressively  larger  and  more 
complex  in  its  convolutions — to  give  greater  battery- 
power,  to  make  a  more  powerful  dynamo — to  work  the 
improved  skeletal  machine.  See,  then,  how  long  it  has 
taken  ISature  to  produce  that  beautiful  finished  article 
we  call  the  horse  ! 

We  have  taken  only  limbs  as  examples  of  what  is  true 
of  the  whole  skeleton.  To  the  superficial  observer  the 
bodies  of  animals  of  different  classes  seem  to  differ  fun- 
damentally in  plan — to  be  entirely  different  machines, 
made  each  for  its  own  j)i^rposes,  at  once,  out  of  hand. 
Extensive  comparison,  on  the  contrary,  show^s  them  to 
be  the  same,  although  the  essential  identity  is  obscured 
by  adaptive  modifications.  The  simplest,  in  fact  the 
only  scientific,  exiDlanation  of  the  phenomena  of  verte- 
brate structure  is  the  idea  of  a  primal  vertebrate,  modi- 


PROOFS  FROM  HOMOLOGIES.  m 

fied  more  and  more  through  successive  generations  by 
the  necessities  of  i^ifferent  modes  of  life. 

See,  then,  in  conclusion,  the  difference  between  man's 
mode  of  working  and  Nature's.  A  man  having  made  a 
steam-engine,  and  desiring  to  use  it  for  a  different  pur- 
pose from  that  for  which  it  was  first  designed  and  used, 
will  nearly  always  be  compelled  to  add  new  parts  not 
contemplated  in  the  original  machine.  Nature  rarely 
makes  new  parts — never,  if  she  can  avoid  it — but,  on  the 
contrary,  adapts  an  old  part  to  the  new  function.  It  is 
as  if  Nature  were  not  free  to  use  any  and  every  device  to 
accomplish  her  end,  but  were  conditioned  by  her  own 
plans  of  structure  ;  as,  indeed,  she  must  be  according  to 
the  derivation  theory.  For  example  :  In  early  Devonian 
times  fishes  were  the  only  representatives  of  the  verte- 
brate type  of  structure.  The  vertebrate  machine  was 
then  a  swimming -machine.  In  the  course  of  time,  when 
all  was  ready  and  conditions  were  favorable,  reptiles  were 
introduced.  Here,  then,  is  a  new  function — that  of  lo- 
comotion on  land.  We  want  a  wallcing-macliine.  Shall 
we  have  a  new  organ  for  this  new  function  ?  No  :  the 
old  swimming-organ  is  modified  so  as  to  adapt  it  for 
walking.  Time  went  on,  until  the  middle  Jurassic,  and 
birds  were  introduced.  Here  is  a  new  and  wonderful 
function,  that  of  flying  in  the  air.  We  want  a  flying- 
machine.  We  know  how  man  would  have  done  this  ;  for 
we  have  the  result  of  his  imagination  in  angels  of  Chris- 
tian art  and  griffins  of  Greek  mythology.  He  would 
have   added   wings  to   already  existing  loarts,   and  this 


112    EVIDENCES   OF   THE  TRUTH   OF  EVOLUTION. 

would  have  necessitated  the  alteration  of  the  whole  plan 
of  structure,  both  skeletal  and  muscular.  Nature  only 
modifies  the  fore-limbs  for  this  new  purpose.  If  we 
must  have  wings,  we  must  sacrifice  fore-legs.  We  can 
not  have  both  without  violating  the  laws  of  morphology. 
Finally,  ages  again  passed,  and,  when  time  was  fully  ri^oe, 
man  was  introduced.  Now  we  want  some  part  to  per- 
form a  new  and  stiU  more  wonderful  function.  We  want 
a  hand,  the  willing  and  efficient  servant  of  a  rational 
mind.  We  know,  again,  how  man  would  have  done  this, 
for  we  have  the  result  in  the  centaurs  of  Greek  mytholo- 
gy, in  which  man's  chest,  and  arms,  and  head  are  added 
to  the  body  of  a  quadruped.  But  natural  laws  must  not 
be  violated,  even  for  man.  If  we  want  hands,  we  must 
sacrifice  feet.  Again,  therefore,  the  fore-limbs  are  modi- 
fied for  this  new  and  exquisite  function.  Thus,  in  the 
fin  of  a  fish,  the  fore-paw  of  a  reptile  or  a  mammal,  the 
wing  of  a  bird,  and  the  arm  and  hand  of  a  man,  we  have 
the  same  part,  variously  modified  for  many  purjDoses. 

Many  other  illustrations  might  be  taken  from  the 
skeleton  and  from  other  systems,  especially  the  muscular 
and  nervous.     But  in  the  muscular  svstem  the  modifica- 

ft/ 

tions  have  been  so  extreme  that  homology  is  much  more 
difficult  to  trace,  and  therefore  requires  more  extensive 
knowledge  than  we  yet  possess,  and  more  extended  com- 
parison than  has  yet  been  attempted.  It  has  been  traced 
with  some  success  through  mammals,  and  probably  will 
be  through  air-breathing  vertebrates — i.  e.,  also  through 
birds,  reptiles,  and  amphibians  ;  but  to  trace  it  through 


PROOFS  FROM  HOMOLOGIES.  113 

fishes  seems  almost  hopeless.  In  the  case  of  the  nervous 
system,  and  especially  of  the  brain,  it  is  again  distinct ; 
but  this  had  better  be  taken  up  under  another  head, 
yiz.,  proofs  from  ontogeny.  Chapter  VI. 

In  the  visceral  organs  homology  is  very  plain,  in  fact 
too  plain.  There  is  not  modification  enough  in  most 
cases  even  to  obscure  it,  because  function  is  the  same  in 
all  animals.  These  organs  do  not,  therefore,  furnish 
good  illustrations  of  that  essential  identity  in  the  midst 
of  adaptive  modification  which  constitutes  the  argument 
for  the  derivative  origin  of  structure.  It  is  the  organs 
of  animal  life  that  show  this  most  perfectly,  because  it 
is  these  that  take  hold  on  the  environment  and  are 
modified  by  it.  There  are,  however,  a  few  striking  illus- 
trations to  be  found  among  the  visceral  organs,  especially 
the  blood-system.  This,  however,  had  better  also  be 
deferred  to  the  chapter  on  ontogeny. 


CHAPTER  V. 

HOMOLOGIES   OF  THE  ARTICULATE   SKELETON. 

We  have  taken  the  vertebrate  skeleton  first,  only  be- 
cause this  department  is  most  familiar.  But  in  reality, 
the  most  beautiful  illustrations  of  essential  identity  of 
structure  in  the  midst  of  infinite  diversity  of  adaptive 
modification  for  different  functions  and  habits  of  life, 
and  therefore  of  common  origin  from  a  primal  form,  are 
found  in  the  department  of  articulates.  I  use  the  old 
Cavierian  department  articulata,  rather  than  the  more 
modern  arthropods^  because  the  former  includes  worms 
also.  Now,  whether  worms  should  be  thus  included  with 
arthropods,  or  deserve  a  whole  department  to  themselves  it 
matters  not  for  our  purposes.  It  is  generally  admitted 
that  arthropods  probably  descended  from  marine  worms. 
They  all  have  the  same  general  plan  of  skeletal  structure. 
It  will  suit  my  purpose,  therefore,  to  regard  worms  as 
the  lowest  form  of  jointed  animals. 

Here,  then,  we  have  an  entirely  different  plan  of 
structure — a  different  style  of  architecture  and  different 
mechanical  principles  of  machinery.  Instead  of  a  skele- 
ton within  and  muscles  acting  on  the  outside,  we  have 


HOMOLOGIES  OF  THE  ARTICULATE  SKELETON.  115 

the  skeleton  on  the  outside,  and  muscles  acting  from 
within.  Instead  of  two  cavities,  a  neural  and  visceral, 
the  skeleton  forms  but  one  cavity,  in  which  all  organs 
are  inclosed  and  protected.  Instead  of  finding  the 
nerve-axis  on  the  dorsal  aspect  of  the  body,  we  find  it  on 
the  ventral  aspect. 

Take  any  articulate  animal,  for  example,  a  shrimp,  a 
cenfciped,  or  a  beetle.  Cut  it  across  the  body,  and  look 
at  the  end  (Fig.  26).     We  see  a  ring  of  bone  (chitin)  in- 


FiG.  26. — Diagram  section  across  an  arthropod,  showing  the  inclosing 
skeleton-ring  and  a  pair  of  jointed  appendages,  n,  nervous  center ; 
V,  viscera  ;  b,  blood  system. 

closing  all  the  organs  (nervous  system  n,  blood  system  b, 
and  visceral  system  v),  and  a  pair  of  jointed  appendages, 
perhaps  legs,  on  each  side.  Now  imagine  these  parts 
repeated  in  a  linear  series.  The  rings  repeated  make  a 
hollow,  jointed  tube  or  barrel,  the  appendages  repeated 
make  a  continuous  row  of  appendages  on  each  side.    Now 


116    EVIDENCES    OF   THE   TRUTH   OF  EVOLUTION. 

this  is  exactly  what  we  actually  find.  The  whole  articu- 
late skeleton  is  ideally  made  up  of  a  series  of  such  re- 
peated rings  and  a23pendages,  modified  according  to  the 
l^osition  in  the  series,  and  the  uses  to  which  they  are 
put.  And  then  the  whole  articulate  department  is  made 
up  of  such  articulate  animals  again  modified  according  to 
place  in  the  scale  of  articulates.  The  modification  in 
the  lower  forms  is  slight,  and  therefore  the  identity  of 
the  repeated  parts  is  obvious  ;  but  as  we  go  up  the  scale, 
and  the  number  and  complexity  of  the  functions  in- 
crease, the  adaptive  modification  becomes  greater  and 
greater,  until  finally  it  so  obscures  the  essential  identity, 
that  it  requires  the  most  extensive  comparison  in  the 
taxonomic  series  and  in  the  ontogenic  scries,  to  pick  up 
the  intermediate  links  and  establish  the  fact  of  common 
origin.  In  a  word,  whether  they  so  originated  or  not,  it 
is  certain  that  the  structure  of  articulate  animals  is  ex- 
actly such  as  would  be  the  case  if  all  these  animals  were 
genetically  connected,  and  came  originally  from  a  primal 
form  something  like  one  of  the  lower  crustaceans,  or, 
perhaps,  a  marine  worm. 

It  will  be  best  to  take  an  example  from  about  the 
middle  of  the  scale,  where  the  two  elements,  viz.,  essen- 
tial identity  and  adajotive  modification,  are  somewhat 
evenly  balanced,  and  both  traceable  with  ease  and  cer- 
tainty. Take,  then,  a  cray-fish,  a  lobster,  or  a  shrimp. 
This  animal  (Fig.  27)  has  twenty  or  twenty-one  rings 
and  pairs  of  jointed  appendages.  The  rings  are  some 
of    them  diminished,    some  of  them   increased  in   size. 


HOMOLOGIES  OF  THE  ARTICULATE  SKELETON.  117 


Fig.  27. — Shrimp  (Palaemonetes  vulgaris). 


Sometimes  several  are  consolidated  ;  sometimes  several 
are  partially  or  wholly  aborted.  The  appeadages  are 
modified  in  shape  and 
size,  according  to  their 
position,  so  as  to  make 
them  s^yimming-appen- 
dages  (swimmerets), 
walking  -  appendages 
(legs),  eating-append- 
ages (jaws),  and  sense- 
appendages  (antennas).  For  example,  in  the  abdomi- 
nal region,  or  so-called  tail,  we  have  seven  segments, 
all  being  perfect  movable  rings,  each  with  its  pair  of 
jointed  appendages,  except  the  last,  or  telson.  The 
appendages  of  the  first  ring  (Fig.  28,  B)  are  specially 
modified  in  the  male  as  organs  of  copulation  (B').  The 
next  four  pairs  are  modified  for  swimmerets  (D')  and 
for  use  as  holders  of  the  eggs  in  the  female.  The  ap- 
pendages of  the  sixth  ring  (G)  are  broad  and  paddle- 
shaped,  and,  together  with  the  telson  or  seventh  ring 
(H),  form  the  powerful  terminal  swimmer.  Going, 
now,  to  the  cephalo-thorax  :  in  this  either  a  large  num- 
ber of  segments  (thirteen  or  fourteen)  are  consolidated 
above  to  form  the  upper  shell  or  carapace  ;  or  else,  as 
is  more  probable,  two  or  three  of  the  anterior  seg- 
ments have  enlarged  and  grown  backward  over,  and  at 
the  expense  of  the  others,  to  form  this  shell.  At  any 
rate,  it  is  certain  that  the  carapace  is  formed  of  the 
dorsal  portions  of   a  number  of   segments   consolidated 


Fig.  28. — External  anatomy  of  the  lobster  (after  Kingsley). 


HOMOLOGIES  OF  THE  ARTICULATE  SKELETON.  119 


together.  Below, 
however,  the  seg- 
ments are  all  dis- 
tinct, and  have 
each  its  own  pair 
of  appendages. 
For  example,  go- 
ing forward  in 
this  region,  the 
five  next  -pnh's  of 
appendages  are 
greatly  enlarged 
and  very  strong, 
and  serve  the  pur- 
pose of  locomo- 
tion. They  are 
icalMng  -  append- 
ages. The  next 
two  or  three  pairs 
are  smaller  and 
somewhat  modi- 
fied, but  not  so 
much  as  to  ob- 
scure their  essen- 
tial similarity  to 
legs.  Like  legs, 
they  are  many- 
jointed,  and  like 
legs,     too,     they 


13 


Oi 


Dt 


C5 


'^J'^^TTVa 


120    EVIDENCES   OF  THE   TRUTH   OF  EVOLUTION. 

have  gills  attached  to  them.  Thej  are  called  maxilli- 
peds,  or  jaw-feet.  They  are  used  like  hands  to  gather 
food  and  carry  it  to  the  mouth.  They  are  gatliering- 
cqjpendages.  Then  follow  three  or  four  pairs  still  more 
modified^  and  used  for  mastication.  They  are  called 
maxillae  and  mandibles.  They  are  eating -appendages. 
Then  follow  two  pairs,  long,  man3'-jointed,  with  the 
same  kind  of  curious  hinge-joints,  which  we  have  in 
the  legs,  undoubtedly  homologous  with  all  the  others, 
but  used  for  an  entirely  different  purjoose,  and  special- 
ly modified  for  that  purpose.  They  are  the  antennas. 
They  are  delicate  organs  of  touch  and  of  hearing,  for 


Fig.  31. — Vibilia,  an  arnpliibod  crustacean  (after  Milne  Edwards). 

the  ear  is  situated  in  the  basal  joint  of  the  ar.terior 
pair.  Last  of  all,  there  is  still  another  pair,  jointed  and 
movable,  on  the  ends  of  which  are  situated  the  eyes. 
These  last  three,  therefore,  are  sense-appendages.     Some 


HOMOLOGIES  OF  THE  ARTICULATE   SKELETON.  121 

writers  make  this  last  pair  special  organs,  not  homolo- 
gous with  appendages. 

For  the  sake  of  greater  distinctness,  we  give  the 
whole  series  of  these  appendages  in  one  of  the  higher 
forms,  viz.,  the  prawn  (Palemon,  Fig.  29,  and  in  one  of 
the  lower  forms,  Nebalia,  Fig.  30). 


Fig.  82. — Lithobius  forclpatus  (after  Carpenter). 

That  these  are  really  homologous  parts  is  further 
shown  by  the  fact  that  in  the  case  of  other  crustaceans, 
such  as  limulus,  the  same  appendages,  i.  e.,  the  append- 
ages of  the  same  body  segments,  which  in  the  cases  be- 
fore mentioned  are  used  as  feet,  become  swimmers,  while 
the  appendages  corresponding  to  jaw-feet  become  walk- 
ers ;  and  even  what  corresponds  to  antennae  or  sense- 
appendages,  may,  as  in  branchippus,  become  powerful 
claspers.  Finally,  in  all  the  lowest  crustaceans,  the 
identity  is  evident,  because  all  the  segments  and  their 
appendages  are  much  alike  in  form  and  function  (Fig. 
31). 

We  have  taken  exaaiples  from  near  the  middle  of  the 
articulate  scale,  because,  as  already  stated,  both  the  essen- 
tial identity   and  the  adaptive  modifications   are   easily 


122    EVIDENCES  OF  THE  TRUTH  OF  EVOLUTION". 

traced.  If  we  go  downward  in  the  scale,  the  structure 
becomes  more  and  more  generalized,  and  the  rings  and 
appendages  become  more  and  more  alike  (Fig.  31),  until 
in  the  most  generalized  forms  we  have  only  a  series  of 
similar  rings,  with  similar  pairs  of  appendages,  except 
some  necessary  modifications  to  form  the  head  and  tail. 
This  is  well  shown  in  the  centiped  (Fig.  32),  and  still 
better  in  marine  worms  (Fig.  33).  In  some  marine 
worms  the  slight  modification  to  form  the  head  takes 


Fig.  33. — Syllis  prolifera. 

place  under  our  very  eyes.  These  often  multiply  by  di- 
viding themselves  into  two.  When  they  do  so,  they  make 
a  new  head  and  new  tail  by  slight  modification  of  seg- 
ments and  appendages  (Fig.  33). 

If,  on  the  other  hand,  we  go  up  the  scale,  we  find 
adaptive  modifications  obscuring  more  and  more  the 
simple  and  obvious  identity  of  parts,  until  finally  the 
identity  can  not  be  recognized  without  extensive  com- 
parison in  the  taxonomic  series  and  study  of  embryonic 
conditions.  In  crabs— which  is  a  higher  form  than  cray- 
fisli — the  tail  or  abdomen  seems  to  be  wanting,  but  is  only 
very  sijpiall  and  bent  under  the  body  and  thus  concealed. 
In  all  essential  respects  the  structure  is  precisely  like  the 


HOMOLOGIES  OF  THE  ARTICULATE  SKELETON.  123 

cray-fish.  In  fact,  in  the  embryo,  we  trace  the  one  form 
into  the  other  ;  for  the  crab  is  at  first  a  long-tailed  crus- 
tacean (Fig.  34). 

Insects  are  the  highest  form  of  articulates.     In  these, 
therefore,  we  find  the  modification  is  still  greater  than  in 


Fig.  34. — Development  of  Carcinus  moenas.     a,  zosea  stage  ;  b,  megalopa 
stage  ;  c,  final  state  (after  Couch). 

crustaceans,  though   even  here   the  ring-and-appendage 
structure  is  plain  enough  in  most  cases. 

One  of  the  best  evidences  of  high  grade  among  ani- 
mals is  the  gathering  of  the  segments  into  distinct 
groups,  and  especially  the  distinctness  of  the  head  as  one 
of  these  groups.  In  worms  and  lower  crustaceans  there 
is  no  grouping  at  all,  the  skeleton  being  a  continuous 
series  of  joints,  only  slightly  modified  at  the  anterior 
and  posterior  extremities.  In  the  higher  Crustacea,  and 
in  spiders  and  scorpions,    they  are   grouped   into  two 


124    EVIDENCES   OF   THE   TRUTH   OF  EVOLUTION. 


Gjvt&ivn^ 


Tarsus^s^       Talmas 

-«         C"\  ^rotVvova)C. 


J) 


/ 


^A^     ScuUVlum  .(^ 


Steymle.   ^ 


U.p.  ^ 


Fig.  35. — External  anatomy  of  Caloptenus  spretus,  the  head  and  thorax 
disjointed  ;  up,  uiopatagium  ;  /,  furcula ;  c,  cercus  (drawn  by  J.  T. 
Kingsley). 


HOMOLOGIES  OF  THE  ARTICULATE  SKELETON.  125 

regions,  viz.,  cephalo-thoras  and  abdomen.  In  insects 
they  arc  grouped  into  three  yery  distinct  regions — head, 
thorax,  and  abdomen.  In  insects,  therefore,  we  find  for 
the  first  time  the  head  distinctly  separated  from  the  rest 
of  the  body.  This  is  an  evidence  of  high  grade,  because 
it  shows  the  dominance  of  head-functions. 

The  insect,  such,  for  example,  as  a  grasshopper,  con- 
sists of  seventeen  or  eighteen  segments  (Fig.  35).  Of 
these,  four  belong  to  the  head,  three  to  the  thorax,  and 
about  ten  to  the  abdomen.  Those  of  the  abdomen  are 
all  separated  and  movable  ;  those  of  the  thorax  and  head 
are  more  or  less  consolidated.  The  appendages  of  the 
head-segments  become  antennse  and  jaw-parts,  1.  e.,  mandi- 
bles— maxilla  and  labium  ;  the  appendages  of  the  thorac- 
segments  become  legs  (the  wings  are  not  homologous 
with  appendages),  while  those  of  the  abdomen  are  aborted. 
The  steps  of  the  gradual  consolidation  on  the  one  hand, 
and  the  abortion  on  the  other,  mav  be  traced  in  the  em- 
bryo  or  larva — i.  e.,  in  the  caterpillar  or  the  grub  of  a 
bee  or  a  beetle.  In  the  caterpillar,  for  example,  there  is 
no  grouping  into  three  regions,  there  is  no  consolida- 
tion, and  all  the  segments  have  appendages.  Again,  the 
almost  infinite  variety  in  the  mouth-parts  among  in- 
sects, brought  about  by  adaptive  modifications  for  biting, 
for  piercing,  and  for  sucking,  and  yet  the  essential  iden- 
tity of  all  to  the  more  simple  and  generalized  structure 
of  the  grasshopper,  is  an  admirable  illustration  of  the 
same  principle.  But  to  dwell  upon  these  minor  points 
would  carry  us  too  far. 


126    EVIDENCES    OF   THE   TRUTH   OF  EVOLUTION. 

Illustration  of  the  Law  of  Differentiation.— We  have 
here,  in  the  modifications  of  segments  and  appendages  of 
articulates,  an  admirable  illustration  of  the  most  funda- 
mental law  of  evolution,  viz.,  the  law  of  differentiation. 
As  we  have  already  seen  (page  21),  perhaps  the  most 
beautiful  and  certainly  the  most  fundamental  illustra- 
tion of  this  law  is  found  in  the  development  of  cell- 
structure.  Commencing  in  the  lowest  animals,  and  in 
the  earliest  embryonic  stages  of  the  higher  animals, 
from  a  condition  in  which  all  are  alike,  the  cells  as  w^e 
go  upward  quickly  diverge  into  different  forms  to  pro- 
duce different  tissues  and  perform  different  functions. 
Here,  then,  we  have  a  perfect  example  of  essential  iden- 
tity and  adaptive  modification.  It  is  the  very  best  type 
of  differentiation.  So  also  skeletal  segments,  commenc- 
ing, in  the  lowest  articulates  and  in  earliest  embryonic 
stages  of  the  higher,  all  alike,  as  we  go  upward  in  either 
series,  begin  immediately  to  diverge  in  various  directions 
(divergent  variation),  taking  different  forms  to  subserve 
different  uses.  Here,  again,  therefore,  is  an  illustration 
of  the  law  of  differentiation.  Lastly,  in  the  articulate 
department,  commencing  with  the  lowest  forms  and  earli- 
est embryonic  conditions,  and  we  may  add  earliest  geo- 
logical times,  and  going  up  either  series  from  generalized 
forms  very  much  alike,  the  individuals  are  gradually 
differentiated  into  many  special  forms,  in  order  to  adapt 
them  to  the  diversified  modes  of  life  actually  found  in 
nature.  Thus  cells,  segments,  individuals,  are  all  alike 
affected  by  this  most  fundamental  law. 


HOMOLOGIES  OF  THE  ARTICULATE  SKELETON.  127 

We  have  taken  our  illustrations  from  only  the  two  de- 
partments of  vertebrata  and  articulata,  because  these  are 
the  most  familiar  to  the  reader,  and  also  have  been  most 
carefully  studied.  We  have  shown  that  the  general 
structure  of  all  vertebrates  is  precisely  what  it  would  be  if 
they  all  had  come  from  one  primal  vertebrate  form,  and 
that  of  all  articulates  what  it  would  be  if  all  had  come 
from  one  primal  articulate  form.  The  only  natural  ex- 
planation, and,  therefore,  the  only  scientific  explanation 
of  this,  is  that  they  loere  really  thus  derived.  The  same 
kind  of  evidence  may  be  drawn  from  the  study  of  other 
departments,  but  to  pursue  the  subject  any  further  in 
this  direction  would  carry  us  beyond  the  limits  which 
we  have  assigned.  We  desire  only  to  explain  the  nature, 
not  to  give  all,  of  the  evidence.  The  examples  given  will 
be  sufficient  for  the  purposes  of  illustration.  The  whole 
proof  is  nothing  less  than  the  whole  science  of  compara- 
tive anatomy. 

Vertebrates,  then,  were  derived  from  a  primal  verte- 
brate, articulates  from  a  primal  articulate,  and  so  for  other 
departments.  But  whence  were  these  jormcf/^  derived  ? 
Are  there  any  intermediate  links  between,  any  deeply 
concealed  common  plan  of  structure  underlying  these 
primary  groups,  showing  a  common  origin  ?  It  must  be 
confessed  that,  in  their  mature  condition,  there  seems  to 
be  but  little  evidence  of  such.  These  .primary  groups 
seem  to  be  built  on  different  plans,  to  be  fundamentally 
of  different  styles  of  architecture.     Therefore  Darwin,  in 

the  true  spirit  of  inductive  caution — that  true  scientific 
7 


128    EVIDENCES   OF  THE  TRUTH   OF  EVOLUTION 

spirit  which  keeps  strictly  within  the  limits  of  evidence 
— commences  with  four  or  five  distinct  primal  kinds, 
from  which  by  divergent  variation  all  animals  were  de- 
scended. Nevertheless,  the  truly  scientific  biologist 
must  ever  strongly  incline  to  believe  that  these  also 
came  from  some  yrimdl  animal,  and  even  that  both 
animals  and  plants  were  derived  from  some  primal  form 
of  living  tiling ;  that  as,  in  the  taxonomic  series,  the 
animal  and  vegetal  kingdoms  in  their  lowest  forms 
merge  undistinguishably  into  one  another;  as  in  the 
ontogenic  series  the  animal  and  plant  germ  are  one, 
so  also  in  the  phylogenic  series  the  earliest  organisms 
were  simply  living  things,  but  not  distinctively  ani- 
mal nor  vegetal.  Science,  therefore,  whose  mission  is  to 
trace  origins  as  far  back  as  possible,  must  ever  strive  to 
find  connecting  links  between  the  primary  groups.  Some 
such  have  been  supposed  to  have  been  discovered.  Some 
find  the  origin  of  vertebrates  among  the  molluscoids  (as- 
cidians) ;  some  find  the  origins  of  both  vertebrates  and 
articulates  among  marine  worms  (annelids).  This  point 
is  still  too  doubtful  to  be  dwelt  upon  here.  It  may  be 
that  we  seek  in  vain  for  such  connecting  links  among 
existing  forms.  It  may  well  be  that  the  point  of  separa- 
tion of  these  great  primary  groups  (unless  we  except 
vertebrates)  was  far  lower  even  than  these  low  forms. 
Both  phylogeny  and  ontogeny  seem  to  indicate  this.  In 
the  earliest  fauna  known,  the  primordial  (for  if  there  was 
life  in  the  archaean  it  was  not  yet  differentiated  into  a 
fauna),  all  the  great  departments,  except  the  vertebrates. 


HOMOLOGIES  OF  THE  AETICULATE  SKELETOiT.  129 

seem  to  have  been  represented.  In  embryonic  develop- 
ment, too,  the  point  of  connection  or  even  of  similarity, 
between  the  great  departments,  is  found,  as  we  shall  see 
hereafter,  only  in  the  earliest  stages — i.  e.,  lower  down 
than  any  but  the  lowest  existing  forms,  viz.,  the  pro- 
tozoa. 


CHAPTER  YI. 

PKOOFS    FKOM    EMBRYOLOGY,     OR    COMPARISOi^     li^     THE 

ONTOGEJTIC    SERIES. 

It  is  a  curious  and  most  significant  fact  that  the  suc- 
cessive stages  of  the  development  of  the  indiviclttal  in  the 
higher  forms  of  any  group  (ontogenic  series)  resemble 
the  stages  of  increasing  complexity  of  differentiated 
structure  in  ascending  the  animal  scale  in  that  group 
(taxonomic  series),  and  especially  the  forms  and  structure 
of  animals  of  that  group  in  successive  geological  epochs 
(phylogenic  series).  In  other  words,  the  individual 
higher  animal  in  embryonic  development  passes  through 
temporary  stages,  which  are  similar  in  many  respects  to 
permanent  or  mature  conditions  in  some  of  the  lower 
forms  in  the  same  group.  To  give  one  example  for  the 
sake  of  clearness  :  The  frog,  in  its  early  stages  of  embry- 
onic development,  is  essentially  a  fish,  and  if  it  stopped 
at  this  stage  would  be  so  called  and  classed.  But  it  does 
not  stop  ;  for  this  is  a  temporary  stage,  not  a  permanent 
condition.  It  passes  through  the  fish  stage  and  through 
several  other  temporary  stages,  which  we  shall  explain 
hereafter,  and  onward  to  the  highest  condition  attained 


PROOFS  FROM  EMBRYOLOGY.       131 

by  amphibians.  Now,  if  we  could  trace  perfectly  the 
successive  forms  of  amphibians,  back  through  the  geo- 
logical epochs  to  their  origin  in  the  Carboniferous,  the 
resemblance  of  this  series  to  the  stages  of  the  deyelop- 
ment  of  a  frog  would  doubtless  be  still  closer.  Surely 
this  fact,  if  it  be  a  fact,  is  wholly  inexplicable  except  by 
the  theory  of  derivation  or  evolution.  The  embryo  of  a 
higher  animal  of  any  group  passes  now  through  stages 
represented  by  lower  forms,  because  in  its  evolution  (phy- 
logeny)  its  ancestors  did  actiudly  have  these  forms.  From 
this  point  of  view  the  ontogenic  series  (individual  his- 
tory) is  a  brief  recapitulation,  as  it  were,  from  memory, 
of  the  main  points  of  the  philogenic  series,  or  family  his- 
tory. We  say  brief  recapitulation  of  the  main  points, 
because  many  minor  points  are  dropped  out.  Even  some 
main  points  of  the  earliest  stages  of  the  family  history 
may  be  dropped  out  of  this  sort  of  inherited  memory. 

This  resemblance  between  the  three  series  must  not, 
however,  be  exaggerated.  Not  only  are  many  steps  of 
phylogeny,  especially  in  its  early  stages,  dropped  out  in 
the  ontogeny,  but,  of  course,  many  adaptive  modifica- 
tions for  the  peculiar  conditions  of  embryonic  life  are 
added.  But  it  is  remarkable  how  even  these — for  exam- 
ple the  umbilical  cord  and  placenta  of  the  mammalian 
embryo — are  often  only  modifications  of  egg-organs  of 
lower  animals,  and  not  wholly  new  additions.  It  is  the 
similarity  in  spite  of  adaptive  modifications  that  shows 
the  family  history. 

We  will  now  illustrate  by  a  few  striking  examples. 


132    EVIDENCES   OF  THE   TRUTH   OF  EVOLUTION". 

We  can  not  do  better  than  to  take,  again,  as  our  first 
example,  the  development  of  tailless  amphibians,  and 
dwell  a  little  more  upon  it  : 

1.  Ontogeny  of  Tailless  Amphibians.— It  is  well 
known  that  the  embryo  or  larva  of  a  frog  or  toad,  when 
first  hatched,  is  a  legless,  tail-swimming,  water-breathing, 
gill-breathing  animal.  It  is  essentially  a  fish,  and  would 
be  so  classed  if  it  remained  in  this  condition.  The  fish 
retains  permanently  this  form,  but  the  frog  passes  on. 
Next,  it  forms  first  one  pair  and  then  another  pair  of 
legs ;  and  meanwhile  it  begins  to  breathe  also  by  lungs. 
At  this  stage  it  breathes  equally  by  lungs  and  by  gills, 
i.  e.,  both  air  and  water.  Now,  the  lower  forms  of  am- 
phibians, such  as  siredon,  menobranchus,  siren,  etc.,  re- 
tain permanently  this  form,  and  are  therefore  called 
perennibranchs,  but  the  frog  still  passes  on.  Then  the 
gills  gradually  dry  up  as  the  lungs  develop,  and  they  now 
breathe  wholly  by  lungs,  but  still  retain  the  tail.  Now 
this  is  the  permanent,  mature  condition  of  many  amj^hi- 
bians,  such  as  the  triton,  the  salamander,  etc.,  which  are 
therefore  called  cadiicihranclis,  but  the  frog  still  passes  on. 
Finally,  it  loses  the  tail,  or  rather  its  tail  is  absorbed  and 
its  material  used  in  further  development,  and  it  becomes 
a  perfect  frog,  the  highest  order  (ajioura)  of  this  class. 

Thus,  then,  in  ontogeny  the  fish  goes  no  further  than 
the  fish  stages.  The  perennibranch  passes  through  the 
fish  stage  to  the  perennibranch  amphibian.  The  caduci- 
branch  takes  first  the  fish-form,  then  the  perennibranch- 
form^  and  finally  the  caducibranch-form,  but  goes  no 


PROOFS  FROM  EMBRYOLOGY.       133 

further.  Last,  the  anoura  takes  first  the  fish-form,  then 
that  of  the  perennibranch,  then  that  of  the  caduci- 
branch,  and  finally  becomes  anoura.  This  is  shown  in 
the  diagram,  which  must  be  read  upward,  line  by  line. 

FISH.  PERENNIBRANCH.  CADUCI  BRANCH.  ANOURA. 


FISH.  PERENNIBRANCH.  CADUCIBRANCH. 


FISH.  PERENNIBRANCH. 


FISH. 

Diagram  showing  the  stages  of  development  of  amphibians.    (To  be  read 

upward.) 

Now,  this  is  undoubtedly  the  order  of  succession  of 
forms  in  geological  times — i.  e.,  in  the  phylogenic  series. 
This  series  is  indicated  by  the  arrows  in  the  diagram. 
Fishes  first  appeared  in  the  Devonian  and  Upper  Silurian 
in  very  reptilian  or  rather  amphibian  forms.  Then  in 
the  Carboniferous,  fishes  still  continuing,  there  appeared 
the  lowest — i.  e.,  most  fish-like — forms  of  amphibians. 
These  luere  undouMedly  perennihranclis.  In  the  Per- 
mian and  Triassic  higher  forms  ajDpeared,  which  were  cer- 
tainly caducibranch.  Finally,  only  in  the  Tertiary,  so  far 
as  we  yet  know,  do  the  highest  form  (anoura)  appear. 
The  general  similarity  of  the  three  series  is  complete. 
If  we  read  the  diagram  horizontally,  we  have  the  onto- 
genic  series  ;  if  diagonally  with  the  arrows,  we  have  both 
the  taxonomic  and  the  phylogenic  series. 

2.  Aortic  Arches. — But  some  will,  perhaps,  say  that 
these  stages  in  the  ontogeny  are  only  examples  of  adapt- 


131    EVIDENCES   OF   THE   TRUTH   OF  EVOLUTION. 


ive  modifications — like  modifications  for  like  conditions 
of  life — and  had  better  be  accounted  for  in  this  way, 
without  reference  to  family  history.  We  will,  therefore, 
take  another  example,  which  can  not  be  thus  accounted 
for — an  example  in  which  there  is  no  possible  use  now 
for  the  peculiar  form  or  structure  which  we  find.     For 

this  purpose  we  take  the 
case  of  the  course  of  circu- 
lation in  vertebrates. 

If  one  examines  the  large 
vessels  going  out  from  the 
Leart  of  a  lizard,  he  will  find 
six  aortic  arches  —  i.  e., 
three  on  each  side.  These 
all  unite  below  to  form  the 
one  descending  abdominal 
aorta.  This  is  shown  in  the 
accompanying  figure  (Fig. 
36),  in  which  a  a'  a"  and 
I  V  b"  are  the  six  arches. 
Now,  there  is  no  conceiva- 
ble use  in  having  so  many 
aortic  arches.  We  know 
this,  because  there  is  but 
one  in  birds  and  mammals, 
and  the  circulation  is  as 
effective,  nay,  much  more  effective  in  these  than  in 
reptiles.  The  explanation  of  this  anomaly  is  revealed 
at  once  as  soon  as  we  examine  the  circulation  of  a  fish, 


Fig.  36. — Showing  heart  and  out- 
going blood-vessels  of  a  lizard 
(after  Owen).  The  arrows 
show  the  course  of  the  blood. 


PROOFS  FROM  EMBRYOLOGY. 


135 


which  is  shown  in  the  accompanying  figure  (Fig.   37). 
The    multiplication    of    the   aortic    arches   is    here,    of 

A  B 


Fig.  o7. — a,  heart  and  gill-arches  of  a  fish ;  b,  one  arch  with   fringe 

(after  Owen) ;  H,  the  heart. 

course,  necessary,  for  they  are  the  gill-arclies.  The 
whole  of  the  blood  passes  through  these  arches,  to  be 
aerated  in  the  gill-fringes.  The  use  of  this  peculiar 
structure  is  here  obvious  enough.  If  a  lizard  were  eyer 
a  fish,  and  afterward  turned  into  a  lizard,  changing  its 
gill-respiration  for  lung-respiration,  then,  of  course,  the 
useless  gill-arches  would  remain  to  tell  the  story.  Now, 
although  a  lizard  never  was  a  fish,  in  its  individual  his- 
tory or  ontogeny,  it  was  a  fish  in  its  family  history  or 
phylogeny,  and  therefore  it  yet  retains,  by  heredity,  this 
curious  and  useless  structure  as  evidence  of  its  ancestry. 

That  this  is  the  true  explanation  is  demonstrated  by 
the  fact  that  in  amphibians  this  very  change  actually 


13G    EVIDENCES   OF   THE   TRUTH   OF  EVOLUTION. 

takes  place  before  our  eyes  in  the  individual  history.  We 
have  already  seen  that  the  individual  frog,  in  its  tadpole 
state,  is  a  gill-breather.     It  has  therefore  its  gill-arches 


Fig.  39. 

Figs.  38,  39, — Diagrams  showing  tlie  change  of  the  course  of  blood  in 
the  development  of  a  frog.  38.  The  tadpole  stage.  39.  The  mature 
condition,  h,  heart ;  gg'g",  external  gills  ;  y^'^",  internal  gills; 
c  c,  connecting  branches  in  the  tadpole ;  pp,  pulmonary  branches. 


PKOOFS   FPwOM  EMBRYOLOGY.  I37 

(Fig.  38),  three  on  each  side,  like  a  fish,  and  for  the  same 
reason,  yiz.,  the  aeration  of  the  blood.  But  when  its  gills 
dry  up  and  lung-respiration  is  established,  its  now  useless 
gill-arches  still  remain  as  aortic  arches,  to  attest  their 
previous  condition  (Fig.  39).  Now,  the  lizard  undoubt- 
edly came  from  an  air-breathing,  tailed  ampliibian,  and 
therefore  inherited  this  form  of  arterial  distribution.  In 
both  lizard  and  amphibian  the  ultimate  cause  is  an  origin 
from  fishes,  in  which  such  arches  are  obyiously  necessary. 
The  diagrams.  Figs.  38  and  39,  are  illustrations  some- 
what idealized,  showing  the  manner  in  which  the  change 
actually  takes  place  in  air-breathing  amphibians.  Fig. 
38  represents  the  tadpole  stage,  and  Fig.  39  the  mature 
condition.  In  the  former  the  gills  are  mostly  external, 
GG',  etc.,  but  also  internal,  gg',  as  in  the  fish.  Observe 
in  this  condition  the  small  connecting  vessels,  cc'.  When 
the  external  gills  dry  up,  these  are  enlarged,  and  tlie 
whole  of  the  blood  passes  through  them,  as  shown  in 
Fig.  39.  It  is  seen,  also,  in  Fig.  38,  that  a  small  branch, 
p,  goes  from  the  lower  gill-arches  to  the  yet  rudimentary 
lung,  /.  When  the  gill-fringes  have  disappeared,  the 
whole  of  the  blood  of  the  lower  arch  goes  through  the 
now  enlarged  pulmonary  branch  to  the  lungs,  L,  now  in 
full  activity,  and  the  remainder  of  this  arch  disappears, 
as  shown  by  the  dotted  lines  in  Fig.  39. 

The  change  which  actually  took  place  in  the  family 
history  of  the  lizard  probably  differed  from  the  above 
only  in  being  more  simple,  the  gills  being  only  internal 
like  the  fish.     The  external  gills  complicate  the  process 


138    EVIDENCES   OF  THE   TRUTH   OF  EVOLUTION. 

a  little  in  the  case  of  the  frog,  but  the  principle  is  pre- 
cisely the  same. 

As  already  explained  (pages  82-85),  the  large  gap  be- 
tween fishes  and  reptiles,  as  regards  mode  of  respira- 
tion, is  completely  filled  both  in  the  taxonomic  series 
— i.  e.,  in  ganoids,  dipnoi,  and  the  mature  condition  of 
the  different  orders  of  amphibians — and  in  the  ontogeny 
of  the  higher  amphibians.  Now,  we  add  that  the  same 
is  true  of  the  arterial  distribution.  We  have  just  traced 
the  change  in  the  ontogeny  of  the  frog,  but  the  steps  of 
the  same  change  are  traceable  in  passing  from  the  typical 
fish  (teleosts),  through  dipnoi  and  amphibians  to  rep- 
tiles. Thus,  again,  the  phylogeuy,  the  taxonomy,  and 
the  ontogeny,  are  in  complete  accord. 

But  the  argument  for  eyolution  does  not  stop  here. 
If  birds  and  mammals  have  come  from  reptiles,  and 
therefore  from  fishes,  we  may  expect  to  find  some  evi- 
dences of  the  same  kind  still  lingering  in  the  great  arter- 
ies. And  such  we  do  find.  It  is  a  most  curious  and 
significant  fact  that,  in  the  early  embryonic  condition  of 
birds  and  mammals,  including  man  himself,  we  find 
on  each  side  of  the  neck  several  gill-slits,  each  with  its 
gill-arch,  and  therefore  several  aortic  arches  on  each 
side,  precisely  similar  to  what  we  have  already  described. 
These  arches  are  subsequently,  some  of  them,  obliterated  ; 
some  modified  to  form  the  one  aortic  arch,  and  some 
of  them  still  more  modified  to  form  the  other  great  arter- 
ies coming  from  the  heart  to  supply  the  head  and  fore- 
limbs. 


PROOFS  FROM  EMBRYOLOGY. 


139 


This  is  so  beautiful  and  convincing  an  example,  and 
one  so  generally  unfamiliar,  to  even  intelligent  persons. 


Fig.  40. — Diagram  of  mammalian  heart,     a,  aorta  ;  p,  pulmonary  artery ; 
scs'c\  subclavium  on  each  side ;  €c\  carotids  on  each  side. 

not  especially  acquainted  with  biology,  that  it  is  best  to 
explain  it  more  fully.  In  Fig.  40  we  give  a  mammalian 
heart  and  outgoing  vessels,  very  slightly  modified,  so  as 
to  suggest  the  process  of  change.  In  Fig.  41  we  give 
an  ideal  diagram  representing  the  primitive  aortic  arches 
as  they  exist  in  the  embryo  of  mammals,  birds,  and 
reptiles.  It  represents,  also,  substantially,  the  arches  as 
they  exist  in  the  mature  condition  in  the  most  reptilian 
fishes  (dipnoi)  and  in  some  sharks,  except  that  in  these 


140    EVIDENCES   OF  THE   TPwUTH   OF  EVOLUTIOIsr. 

the  arches  are  of  course  furnished  with  gill-fringes.     We 
will  use  this  figure,  therefore,  to  rej)resent  both  the  em- 


FiG.  41. — Ideal  diagram  representing 
the  primitive  aortic  arches  (after 
Rathke). 


Fig.  42. — Modified  for  bird. 


bryonic  condition  of  air-breathing  vertebrates  and  the 
mature  condition  of  some  fishes.  The  place  of  the  heart 
is  indicated  by  the  dotted  circle.  Fig.  36,  on  page  134:, 
shows  what  these  arches  become  in  reptiles  (lizard).  It  is 
seen  that  the  two  upper  arches  on  each  side  are  obliterated, 
as  indeed  they  already  are  in  some  teleost  fishes.  Fig.  42 
shows  what  they  become  in  birds.  The  two  upper  arches 
are,  of  course,  obliterated.  The  others  are  all  modified, 
each  in  a  manner  which  may  be  readily  understood  by 


PROOFS   FROM  EMBRYOLOGY. 


Ml 


comparison  with  Fig.  41.  Finally,  Fig,  43  shows  what  they 
become  in  mammals  and  in  man.  In  the  bird  (Fig.  42) 
the  first  pair  of  arches  become  the  two  pulmonary  arteries 
as  they  do  also  in  the  lizard.  The  second  pair  become  on 
the  right  side  (left  of 
the  diagram)  the  aortic 
arch,  on  the  left  side 
(right  of  the  diagram) 
the  left  subclavian,  s'c' 
(the  right  subclavian, 
sc,  is  a  branch  of  the 
aortic  arch).  The  third 
pair  become  carotids, 
cc,  while  the  fourth  and 
fifth,  as  already  said,  are 
aborted.  In  the  mam- 
mal (Fig.  43),  on  the  left 
side  (right  of  the  dia- 
gram) the  first  arch  be- 
comes the  pulmonary 
artery,  p.  In  the  foetus  the  continuation  of  this  arch 
forms  the  ductus  arteriosus,  which  is  afterward  obliter- 
ated, as  shown  in  the  dotted  line.  The  second  arch  be- 
comes the  aortic  arch,  the  third  the  left  exterior  carotid. 
On  the  right  side  (left  of  the  diagram)  the  first  arch 
becomes  aborted ;  the  second,  the  right  subclavian,  sc 
(the  left  subclavian,  s'c',  is  a  branch  of  the  aortic  arch) ; 
and  the  third,  the  right  carotid.  Nos.  4  and  5,  on  both 
sides,  as  usual,  are  aborted. 


Fig.  43. — Modified  for  mammal. 


142    EVIDENCES   OF  THE  TRUTH   OF  EVOLUTION. 


d- 


■711- 


V/^ 


See,  then,  the  gradual  process  of 
change  through  tlie  whole  yertebrate 
department.  In  the  lowest  of  all  yer- 
tebrates,  if  vertebrate  it  may  be  called 
(for  what  corresponds  to  its  backbone 
is  an  unjointed,  fibrous  cord),  the  am- 
phioxus  or  lancelet  (Fig.  44),  there  are 
about  forty  gill-arches  on  each  side. 
As  we  rise  in  the  scale  of  fishes  these 
are  reduced  in  number.  In  the  lam- 
prey, there  are  seven  ;  in  the  sliarks, 
usually  five ;  in  ordinary  fishes  (tele- 
.  osts),  there  are  four  or  sometimes  only 
three  on  each  side,  the  others  being 
aborted.  Thus  far  the  change  is  only 
by  diminution  of  number  in  accordance 
with  a  law  universal  in  biology,  that 
decrease  in  the  number  of  identical 
organs  is  evidence  of  advance  in  the 
grade  of  organization,  provided  that  it 
be  assoT3iated  with  more  perfect  struct- 
ure of  the  organ.  The  further  change 
is  one  of  adaptive  modification.  In 
some  reptiles  (lizard)  the  three  gill- 
arches  on  each  side  all  retain  the  form 
of  aortic  arches  ;  in  some  reptiles  only 
Fig.  44.  —  Lancelet  two   retain   this  form.     In   birds   and 

(Amphioxus    Ian-  .    .       ^     . 

ceoiatus).     Mag-  mammals  only  one  arch  is  retained,  in 
one-half  Umes^^     ^^^^  form  of  aortic  arch,  the  others  be- 


PROOFS  FEOM  EMBRYOLOGY.       I43 

ing  modified  to  form  the  great  outgoing  vessels  of  the 
heart,  or  else  aborted.  It  mav  be  well  to  observe  that  in 
birds  the  one  aortic  arch  turns  to  the  right,  while  in 
mammals  it  turns  to  the  left.  This  is  positive  evidence 
that  mammals  could  not  have  come  from  birds,  nor  vice 
versa.  They  both  came  from  reptiles,  and,  of  the  many 
reptilian  arches,  a  right  one  was  retained  by  the  bird 
branch,  and  a  left  one  by  the  mammalian. 
■  In  all  the  figures  illustrating  this  subject,  we  have  left 
out  the  great  incoming  vessels  or  veins,  because  we  are 
not  here  concerned  with  them,  they  not  being  trans- 
formed gill-arches. 

Last  of  all,  it  may  be  well  to  stop  a  moment  to  show 
the  cogency  of  this  evidence.  If  it  were  a  question  of 
the  origin  of  some  structure  not  only  useful  (for  all  struct- 
ures selected  by  Nature  must  be  useful)  but  the  lest 
imaginable,  like  the"  eye  or  the  ear,  for  example  ;  then,  if 
we  examined  only  the  liigliest  form  or  the  finished  article, 
there  are  two  ways  in  which  it  is  possible  to  explain  the 
adaptive  structure.  We  may  either  suppose  that  it  was 
made  at  once  out  of  hand,  by  some  intelligent  contriver ; 
or  else  that  it  was  slowly  made  by  a  process  of  evolution, 
becoming  more  and  more  perfect  by  a  selection  of  only 
the  most  perfect  from  generation  to  generation.  But  in 
the  case  of  the  six  aortic  arches  of  the  lizard,  we  are  shut 
up  to  the  one  explanation  only,  viz.,  by  slow  process  of 
evolution.  One  arch  is  all  that  is  necessary,  as  is  plainly 
shown  by  the  use  of  only  one  in  the  more  perfect  circula- 
tion of  birds  and  mammals.     If  the  thing  were  done  out 


U4:  evide:nces  of  the  truth  of  evolution 

of   hand,   unconditioned   by  the   previous    structure    in 
fishes,  to  have  made  six  was  surely  but  a  bungling  piece 

of  work. 

3.  Vertebrate  Brain.— Another  excellent  example  is 
the  structure  of  the  vertebrate  brain.  The  brain  of  an 
average  fish  is  represented  in  Fig.  45.     It  consists  of  four 


Fig.  45. — Fish-brain,     a,  side  view  ;  b,  top  view. 

or  five  swellings,  or  ganglia,  strung  along,  one  beyond 
another.  Commencing  behind,  these  are,  first,  the  me- 
dulla, m;  then  the  cerebellum,  cb  ;  then  the  optic  lobes, 
ol ;  then  the  cerebrum  and  thalamus  combined,  cr  j  and 
last,  the  olf active  lobes,  of.  Of  these,  it  will  be  observed, 
the  optic  lobe  is  the  largest  in  the  brain  of  the  fish  (Fig. 
45).     In  the  brain  of  the  reptile  (Fig.  46)  we  have  the 


Fig.  46. — Reptile-brain,     a,  side  view  ;  b,  top  view. 

same  serial  arrangement,  of  the  same  parts,  only  that  the 
cerebrum  has  now  become  the  dominant  part  instead  of 
the  optic  lobes.  In  the  average  bird  (Fig.  47)  the  cere- 
brum has  grown  so  large  that  it  extends  backward,  and 
partly  covers  the  optic  lobes.  In  the  lower  mammals 
(marsupials),  the  brain  is  much  the  same  in  this  respect, 


PROOFS   FROM  EMBRYOLOGY. 


145 


as  in  birds — i.  e.,  the  cerebrum   only  partly   covers   the 
optic  lobes,  so  that,  looked  at  from  above,  the  whole  se- 


FiG.  47,— Bird-brain,     a,  side  view  •  b,  top  view. 

ries  of  ganglia  are  still  visible.     But  in  the  average  mam- 
mal (Fig.  48)  the  cerebrum  is  so  enlarged  that  it  covers 

A  B 


Fig.  48.—  Mammal-brain,     a,  top  view  ;  b,  side  view., 

entirely  the  optic  lobes  and  encroaches  on  the  cerebellum 
behind  and  the  olfactive  lobes  in  front.  In  some  mon- 
keys, indeed,  the  cerebellum  is  nearly  or  even  quite 
covered.     Finally,  in  man  (Fig.  49),  the  cerebrum   has 


Fig.  49. — Man's  brain,     a,  side  view  ;  b,  top  view. 


146    EVIDENCES   OF   THE   TRUTH   OF  EVOLUTION. 


grown  so  enormously  that  it  covers  every  other  part  and 
completely  conceals  them  from  view  when  the  brain  is 
looked  at  from  above.     In  front  it  not  only  covers  but 


r^yWOAV 


Fig.  50. — Ideal  section  showing  all  the  above  stages. 

has  grown  far  bevond  the  olf active  lobes  :  behind  it  ex- 
tends   beyond  and   overhangs   the   cerebellum  ;    on   the 

sides  it  overhangs  and 
covers  all.  Looked  at 
from  above,  nothins:  is 
seen  but  this  great 
ganglion.  The  ideal 
section  (Fig.  50)  rep- 
resents all  these  stages 
diagrammatically     in 


Fig.  51. — Sab-fish  stage,      th,  thalamus; 
o/,  optic  lobs  ;  m,  medulla. 


one  figure.     After  what  has  been   said,  the  figure  will 
be  readily  understood. 


PROOFS   FROM  EMBRYOLOGY. 


147 


Now,  it  is  a  most  remarkable  fact  that  substantially 
these  same  stages,  which  are  permanent  conditions  in  the 


Fig.  52. — Fish-stage,      o/,  olfactive  lobe ;  cr,  cerebrum  ;  th,  thalamus  ; 
ol,  optic  lobe ;  cb,  cerebellum ;  m,  medulla. 

taxonomic  series,  are  passed  through  as  transient  stages  in 
the  embryonic  development  of  the  human  brain,  and  in 
the  order  given  above.  The  very  early  condition  of  the 
human  brain  is  represented  in  Fig.  51.     It  is  evidently 


Fig.  53. — Reptile-stage. 

nothing  more  than  the  intercranial  continuation  of  the 
spinal  cord,  enlarged  a  little  into  three  swellings  or  gan- 
glia. These  are  the  early  representatives  of  the  medul- 
la, the  optic  lobes,  and  the  thalamus  ;  which  last  may 
be  regarded  as  the  basal  and  most  fundamental  part  of 
the  cerebrum.  This  stage  may  be  regarded  as  lower 
than  that  of  the  ordinary  fish.  I  have  called  it,  therefore, 
the  sub-fish  stage.  The  cerebellum  is  a  subsequent  out- 
growth from  the  medulla,  as  is  the  cerebrum  and  olfac- 


148    EVIDENCES   OF   THE   TRUTH   OF  EVOLUTION. 

tive  lobes  from  the  thalamus.  Fig.  52  may  be  said,  there- 
fore, to  represent  "fairly  the  fish-stage.  Henceforward  the 
principal  growth  is  in  the  cerebrum  and  cerebellum, 
both  of  which  are  subsequent  outgrowths  of  the  origi- 
nal simple  ganglia,  the  medulla,  and  the  thalamus.  The 
cerebrum  especially  increases  steadily  in  relative  size,  first 
becoming  larger  than  but  not  coyering  the  optic  lobes 
(Fig.  53).    This  represents  the  reptilian  stage.    Next,  by 


Fig.  54. — Bird-stage,     q/,  olfactive  lobe ;    <rr,  cerebrum  ;    ih^  thalamus ; 
oZ,  optic  lobe ;  cb,  cerebellum ;  m,  medulla. 

further  growth,  it  covers  partly  the   optic  lobes  (Fig. 
54).      This  may    be   called  the    bird-stage.      Then   it 


Fig.  55. — Mammalian  stage. 


PROOFS  FROM  EMBRYOLOGY. 


149 


covers  wholly  the  optic  lobes,  and  encroaches  on  the 
cerebellum  behind  and  olfactive  lobes  in  front  (Fig.  55). 
This  is  the   mammalian   stage.     Finally,  it  covers  and 


Fig.  56. 


-Iluman  stage. 


overhangs  all,  and  thus  assumes  the  human  stage  (Fig. 
56). 

We  have  spoken  thus  far  only  of  relative  size;  but 
progressive  changes  take  place  also  in  complexity  of 
structure — i.  e.,  in  the  depth  and  number  of  convolu- 
tions of  the  cerebrum  and  cerebellum.  The  cerebrums 
of  fish,  of  rejDtile,  bird,  and  lower  mammals  are  smooth. 
About  the  middle  of  the  mammalian  series  it  begins  to 
be  convoluted.  These  convolutions  become  deeper  and 
more  numerous  as  we  go  upward  in  the  scale,  until  they 
reach  the  highest  degree  in  the  human  brain.  The  ob- 
ject of  these  inequalities  is  to  increase  the  surface  of  gray 
matter — i.  e.,  the  extent  of  the  force-generating  as  com- 


150    EVIDENCES   OF   THE  TRUTH   OF  EVOLUTION". 

pared  v\^ith  the  force-transmitting  part  of  the  brain,  or 
battery  as  compared  with  conducting-wire.  Now,  in 
embryonic  development  the  human  brain  passes  also 
through  these  stages  of  increasing  complexity  of  organi- 
zation. Here  also  the  ontogenic  is  similar  to  the  taxo- 
nomic  series. 

Now,  why  should  this  peculiar  order  be  observed  in 
the  building  of  the  individual  brain  ?  We  find  the  an- 
swer, the  only  conceivable  scientific  answer  to  this  ques- 
tion, in  the  fact  that  tliis  is  the  order  of  the  iuilding  of 
the  vertebrate  brain  by  evolution  throughout  geological 
historv.  We  have  alreadv  seen  that  fishes  were  the  only 
vertebrates  living  in  the  Devonian  times.  The  first  form 
of  brain,  therefore,  was  that  characteristic  of  that  class. 
Then  reptiles  were  introduced  ;  then  birds  and  marsu- 
pials ;  then  true  mammals ;  and,  lastly,  man.  The  differ- 
ent styles  of  brains  characteristic  of  these  classes  were, 
therefore,  successively  made  by  evolution  from  earlier 
and  simpler  forms.  In  phylogeny  this  order  was  ob- 
served because  these  successive  forms  were  necessary  for 
perfect  adaptation  to  the  environment  at  each  step.  In 
taxonomy  we  find  the  same  order,  because,  as  already  ex- 
plained (page  11),  every  stage  of  advance  in  phylogeny 
is  still  represented  in  existing  forms.  In  ontogeny  we 
have  still  the  same  order,  because  ancestral  characteris- 
tics are  inherited,  and  family  history  recapitulated  in 
the  individual  history. 

But  not  only  is  this  order  found  in  the  evolution 
of  the  whole  vertebrate  department,  but  something  of 


PROOFS   FROM  EMBRYOLOGY. 


151 


A 


B 


the  same  kind  is  found  also  in  the  evolution  of  each 
class.  The  earliest  reptiles,  the  earliest  birds,  and  the 
earliest  mammals  had  smaller  and  less  perfectly  organ- 
ized brains  than  their  nearest  congeners  of  the  present 
day..  This  is  shown  in  the  accompanying  figures  (Figs. 
57  and  58).  To  carry  out  one  example  more  perfectly  : 
In  the  history  of  the 
horse  family,  in  con- 
nection with  the  chang- 
es of  skeletal  structure 
already  described  (page 
108),  we  have  also  cor- 
responding clianges  in 
the  size  and  structure 
of  the  brain  ;  pari  joas- 
su  with  the  improve- 
ment of  the  mechan- 
ism we  have  also  in- 
creased engine  -  power 
and  increased  muscu- 
lar energy  and  there- 
fore increased  activity 
and  grace.  The  brain 
of  a  modern  horse, 
though  not  very  large, 

is   remarkable   for    the     Fig.  5*7.— a,  brain  of  extinct  Ichthjomis ; 

B,  modern  tern. 

complexity  of  its  con- 
volutions.    The  great  energy,  activity,  and  nervous  ex- 
citability of  the  horse  are  the  result  of  this  structure. 


152    EVIDENCES   OF  THE   TRUTH  OF  EVOLUTIONo 


Fig.  58. — a,  brain  of  Eocene  diuoceras  ;  b,  Miocene  broutothere  ;  c,  mod- 
ern horse. 


PROOFS  FROM  EMBRYOLOGY.       I53 

Cephalization. — Thus,  in  going  up  the  phylogenic, 
the  taxoiiomic,  or  the  ontogenic  series,  we  find  a  gradual 
process  of  development  headward,  brainward,  cerebrum- 
ward  ;  or,  more  generally,  we  might  say  that  in  all  or- 
ganic evolution  we  find  an  increasing  dominance  of  the 
higher  oyer  the  lower,  and  of  the  highest  over  all.  For 
example,  in  the  lowest  plane  of  either  series  we  find  first 
the  different  systems  imperfectly  or  not  at  all  differen- 
tiated. Then,  as  differentiation  of  these  progress,  we 
find  an  increased  dominance  of  the  highest  system — the 
nervous  system;  then  in  the  nervous  system,  the  in- 
creasing dominance  of  its  highest  part — the  hrain ; 
then  in  the  brain  the  increasing  dominance  of  its  high- 
est ganglion — the  cerehriom ;  and,  lastly,  in  the  cere- 
brum the  increasing  dominance  of  its  highest  sub- 
stance— the  exterior  gray  matter — as  shown  by  the  in- 
crea'sing  number  and  depth  of  the  convolutions.  This 
whole  process  may  be  called  cephalization. 

Shall  the  process  stop  here  ?  When  evolution  is 
transferred  from  the  animal  to  the  human  plane,  from 
the  physiological  to  the  psychical,  from  the  involuntary 
and  necessary  to  the  voluntary  and  free,  shall  not  the 
same  law  hold  good  ?  Yes  !  all  social  evolution,  all 
culture,  all  education,  whether  of  the  race  or  the  indi- 
vidual, must  follow  the  same  law.  All  psychical  ad- 
vance is  a  cephalization — i.  e.,  an  increasing  dominance 
of  the  higher  over  the  lower  and  of  the  highest  over 
all ;  of  the  mind  over  the  body,  and  in  the  mind  of 
the  higher  faculties  over  the  lower ;  and,  finally,  the 


154    EVIDENCES   OF  THE   TRUTH   OF  EVOLUTION. 


subordination  of  the  whole  to 
the  highest  moral  purpose. 

4.  Fish-Tails.  —  Still  an- 
other and  last  example  :  It 
has  long  been  noticed  that 
there  are  amons^  fishes  two 
st3^1es  of  tail-fins.  These  are 
the  even-lobed,  orhomocercal 
(Fig.  59),  and  the  uneven- 
lobed,  or  heterocercal  (Fig. 
60).  The  one  is  character- 
istic of  ordinary  fishes  (tele- 
osts),  the  other  of  sharks  and 
some  other  orders.  In  struct- 
ure the  difference  is  even 
more  fundamental  than  in  form.  In  the  former  style 
the  backbone  stops  abruptly  in  a  series  of  short,  enlarged 
joints,    and  thence   sends    off   rays  to  form  the  tail-fin 


Fig.  59. — Horaocercal  tail-fin. 
A,  form  ;  b,  structui'e. 


Fig.  60. — Heterocercal  or  vertcbrated  tail-fin.     a,  form  ;  b,  structure. 


PROOFS  FROM   EMBRYOLOGY. 


155 


(Fig.  59,  b)  ;  in  the  latter  the  backbone  runs  through 
the  fin  to  its  very  point,  growing  slenderer  by  degrees, 
and  giving  off  rays  above  and  below  from  each  joint, 
but  the  rays  on  the  lower  side  are  much  longer  (Fig.  60, 
b).  This  style  of  fin  is,  therefore,  vertehrated,  the  other 
non-vertebrated.  Figs.  59  and  60  show  these  two  styles 
in  form  and  structure.  But  there  is  still  another  style 
found  only  in  the  lowest  and  most  generalized  forms  of 
fishes.  In  these  the  tail-fin  is  vertebrated  and  yet  sym- 
metrical.     This  style  is  shown  in  Fig.  61,  A  and  B. 


B 


Fig.  61. — Vertebrated  but  symmetrical  fin,     a,  form  ;  b,  structure. 

]S"ow,  in  the  development  of  a  teleost  fish  (Fig.  58), 
as  has  been  shown  by  Alexander  Agassiz,*  the  tail-fin  is 
first  like  Fig.  61 ;  then  becomes  heterocercal,  like  Fig.  60 ; 
and,  finally,  becomes  homocercal  like  Fig.  59.  Why  so  ? 
Not  because  there  is  any  special  advantage  in  this  succes- 
sion of  forms  ;  for  the  changes  take  place  either  in  the 
Qgg  or  else  in  very  early  embryonic  states.  The  an- 
swer is  found  in  the  fact  that  tliis  is  the  order  of  change 

*  "Proceedings  of  American  Academy  of  Arts  and  Sciences,"  vol. 
xiv,  May,  1878. 


156    EYIDEXCES   OF  THE   TRUTH   OF  EVOLUTION. 

in  the  pliylogenic  series.  The  earliest  fish-tails  were 
either  like  Fig.  61  or  Fig.  60  ;  never  like  Fig.  59.  The 
earliest  of  all  were  almost  certainly  like  Fig.  61 ;  then 
they  became  like  Fig.  60  ;  and,  finally,  only  much  later  in 
geological  history  (Jurassic  or  Cretaceous),  they  became 
like  Fig.  59.  This  order  of  change  is  still  retained  in 
the  embryonic  development  of  the  last  introduced  and 
most  specialized  order  of  existing  fishes.  The  family  his- 
tory is  repeated  in  the  individual  history. 

Similar  changes  have  taken  place  in  the  form  and 
structure  of  birds'  tails.  The  earliest  bird  known — the 
Jurassic  Archseopteryx  —  had  a  long  reptilian  tail  of 
twenty-one  joints,  each  joint  bearing  a  feather  on  each 
side,  right   and   left  (Fig.  62).     In  the  typical  modern 


Fig.  62. — Tail  of  the  Archseopteryx. 

bird,  on  the  contrary,  the  tail-joints  are  diminished  in 
number,  shortened  up,  and  enlarged,  and  give  out  long 
feathers,  fan-like,  to  form  the  so-called  tail  (Fig.  63). 
The  Archaeopteryx'  tail  is  vertehrated,  the  typical  bird's 
non-vertebrated.  This  shortening  up  of  the  tail  did  not 
take  place  at  once,  but  gradually.  The  Cretaceous  birds, 
intermediate  in  time,  had  tails  intermediate  in  struct- 
ure.    The  Hesperornis  of  Marsh  had  twelve  joints.     At 


PROOFS  FROM  EMBRYOLOGY. 


157 


Fig.  63. — Tail  of  a  modem  bird. 


first — in  Jurassic — the  tail  is  fully  a  half  of  the  whole 
vertebral  column.  It  then  gradually  shortens  up  until 
it  becomes  the  aborted 


organ  of  typical  mod- 
ern birds.  Now,  in 
embryonic  develop- 
ment, the  tail  of  the 
modern  typical  bird 
passes  through  all 
these  stages.  At  first 
the  tail  is  nearly  one 

half  the  whole  vertebral  column  ;  then,  as  development 
goes  on,  while  the  rest  of  the  body  grows,  the  growth  of 
the  tail  stops,  and  thus  finally  becomes  the  aborted  or- 
gan we  now  find.  The  ontogeny  still  passes  through 
tlie  stages  of  the  phylogeny.  The  same  is  true  of  all 
tailless  animals.  The  frog  is  tailed  in  the  larval  condi- 
tion, because  its  ancestors  were  tailed  amphibians.  Even 
man  himself  is  endowed  with  a  much  more  considerable 
tail,  viz.,  eight  or  nine  joints,  in  his  early  embryonic 
condition.* 

We  have  taken  all  our  examples  from  vertebrates, 
but  quite  as  many  and  as  good  examples  might  be  found 
among  articulates.  Insects,  in  the  larval  state,  are 
worm-like  in  form.  Hence  it  is  probable  that  the  ear- 
liest progenitors  of  this  class  were  worm-like.  Again, 
some  insects   have   aquatic   larvae.     The   progenitors  of 

*  Fol.,  "  Archives  des  Sciences,"  vol.  xiv,  p.   84,    1885;  "Science," 
vol.  vi,  p.  92,  1885. 


158    EYIDEXCES   OF   THE   TRUTH   OF   EVOLUTION. 

these — ^in  fact,  of  all  insects — were  i^robably  aquatic. 
Crabs,  in  a  larval  condition,  are  long-tailed,  and  we 
know  tliat  tlie  long-tailed  crustaceans  (Macrourans)  ^^re- 
ceded  the  short-tailed  (Brachyourans).  Water-breathing 
animals  preceded  air-breathers  ;  the  same  is  true  in  the 
ontogeny  of  the  frog,  of  many  insects,  and,  we  might 
add,  even  of  mammals.  For  the  breathing  of  the  fostus 
in  utero  is  essentially  by  exposure  of  foetal  blood  to  the 
oxygenated  blood  of  the  mother  in  a  sort  of  gill- fringes 
(placental  tufts).  But  why  should  we  multii^ly  exam- 
ples ?  Tlie  whole  of  embryology,  in  every  department, 
is  made  up  of  examples  of  the  same  law. 

Illustration  of  the  Differentiation  of  the  Whole  Animal 
Kingdom. — Finally,  the  law  of  differentiation  in  the  evo- 
lution of  the  whole  animal  kingdom  may  be  well  illus- 
trated by  means  of  the  different  directions  taken  in  the 
development  of  the  eggs  of  all  the  various  kinds  of  ani- 
mals. Suppose,  then,  we  have  one  thousand  eggs,  rep- 
resenting all  the  different  departments,  classes,  orders, 
families,  etc.,  of  animals.  Many  of  these  may  doubtless 
be  identified  by  form  or  size,  or  some  other  super- 
ficial character,  as  the  eggs  of  this  or  that  animal, 
hut  structurally  tliey  are  all  alike.  At  first,  i.  e.,  as 
germ-cells,  they  all  represent  the  earliest  coiidition  of 
life  on  the  earth,  and  the  lowest  forms  of  life  noio. 
If  we  now  watch  their  development,  w^e  find  that  some 
remain  in  this  first  condition  without  further  change. 
These  we  set  aside.  They  are  Protozoa.  The  remain- 
der continue  to  develo]^,    but  at  first   it  would  be   im- 


PROOFS  FROM  EMBRYOLOGY.       159 

possible  to  say  to  which  of  the  several  departments  or 
primary  groups  they  each  belonged.  Then,  by  cell-mul- 
tiplication, the  original  single  cell  becomes  a  cell-aggre- 
gate. It  may  be  compared  now  to  a  compound  proto- 
zoan, such  as  Foraminifera.  The  cell-aggregate  then  dif- 
ferentiates into  layers,  and  forms,  in  fact,  a  two-layered 
sac  called  a  gastrula.  This  is  the  structure  of  some  of 
the  lowest  coelenterates,  such  as  the  hydra.  Thus  far  all 
seem  to  go  together.  But  now,  for  the  first  time,  the 
primary  groups  are  declared.  If  it  be  a  vertebrate,  for 
example,  the  most  fundamental  characters  —  the  cere- 
bro-spinal  axis,  the  vertebral  column,  and  the  double 
cavity,  neural  and  visceral,  are  outlined.  Suppose,  now, 
we  set  aside  all  other  departments,  and  fix  our  atten- 
tion on  the  vertebrates.  At  first  we  could  not  tell 
which  were  mammals,  birds,  reptiles,  or  fishes  ;  but  after 
a  while  the  classes  are  declared.  AYe  now  set  aside  all 
other  classes  and  watch  the  mammals.  After  a  while  the 
order  declares  itself.  We  select  the  ungulates.  Then 
the  family  is  declared,  say  the  EquidcB  ;  then  the  genus, 
Equus  ;  and,  lastly,  the  species,  Cahallus.  * 

The  same  would  be  true  if  we  followed  any  other 
line  of  development,  whether  in  vertebrates  or  in  any 
other  department.  Observe,  then,  that,  in  following  any 
one  line  as  we  have  done,  there  is  an  increasing  speciali- 

*  Of  course,  this  is  a  purely  imaginary  case.  The  conditions  of  de- 
velopment of  the  eggs  of  higher  animals  forbid  continuous  watching  the 
process.  Yet  we  do  observe  in  different  individuals  all  these  stages  in 
mammals  as  well  as  other  animals. 


160    EVIDENCES  OF  THE  TRUTH   OF  EVOLUTION. 

zatioHj  and,  if  we  followed  all  the  lines,  an  increasing  dif- 
ferentiation, like  the  branching  and  rebranching  of  a  tree. 
Now,  this  is  the  type  and  illustration  of  what  took  place 
in  the  development  of  the  animal  kingdom.  We  con- 
clude that  the  animal  kingdom  appeared  first  as  Proto- 
zoa, then  as  living  cell-aggregates  or  compound  proto- 
zoans, then  as  gastrula  or  two-la3'ered  sacs  with  oral 
opening.  Then  the  great  primary  departments,  unless 
we  except  the  vertebrates,  commenced  to  separate.  This 
took  place  before  the  primordial  period ;  for  in  the  pri- 
mordial fauna  we  have  all  the  dejiartments,  excej^t  verte- 
brates, already  declared.  This  completely  explains  why 
it  is  that  we  are  able  to  trace  homology  only  within  the 
limits  of  each  primary  group. 

But  the  question  has  doubtless  already  occurred  to 
the  thoughtful  reader,  *'Why  should  the  steps  of  the 
phylogeny  be  repeated  m  the  ontogeny  ?"  The  general 
answer  is  doubtless  to  be  found  in  the  law  of  heredity — 
that  wonderful  law,  so  characteristic  of  living  things. 
We  have  compared  it  to  a  brief  recapitulation  from  mem- 
ory—  the  minor  points,  especially  if  they  be  also  early, 
dropping  out.  But  can  we  not  explain  it  further  ?  It 
is  probable  that  we  find  a  more  special  exj^lanation  in 
'^  the  law  of  acceleration,^^  first  brought  forward  by  Prof. 
Cope.  By  the  law  of  heredity  each  generation  repeats 
the  form  and  structure  of  the  previous,  and  in  the  order 
in  which  they  successively  apj^eared.  But  there  is  a 
tendency  for  each  successively-appearing  character  to  ap- 
pear a  little  earlier  in  each  successive  generation  ;  and 


PROOFS  FROM  EMBRYOLOGY.       IGl 

by  this  means  time  is  left  over  for  the  introduction  of 
still  higher  neiv  characters.  Thus,  characters  which  were 
once  adult  are  pushed  back  to  the  young,  and  then  still 
back  to  the  embryo,  and  thus  place  and  time  are  made 
for  each  generation  to  push  on  still  higher.  The  law  of 
acceleration  is  a  sort  of  young-Americanism  in  the  ani- 
mal kingdom.  If  our  boys  acquire  knowledge  and  char- 
acter similar  to  that  of  adults  of  a  few  generations  back, 
they  will  have  time  while  still  young  and  plastic  to  press 
forward  to  still  higher  planes. 

Proofs  from  Rudimentary  and  Useless  Organs. — These 
have  to  a  large  extent  been  anticipated  under  previous 
heads.  The  tails  of  birds  and  the  gill-arches  of  reptiles 
are  rudimentary.  The  finger-bones  of  a  whale's  paddle 
or  a  turtle's  flipper  may  be  regarded  as  useless,  at  least 
so  far  as  the  exact  number  of  constituent  pieces  is  con- 
cerned ;  for  an  extended  surface,  without  visible  joints 
or  separate  fingers,  is  all  that  is  seen,  and  apparently  all 
that  is  required.  The  splint-bones  of  a  horse's  foot  or 
the  dew-claws  of  a  dog's  foot  are  certainly  useless.  We 
have  already,  in  speaking  of  modifications  of  structure 
and  of  embryonic  conditions,  given  many  examples  of 
this  kind,  but  it  may  be  well  to  add  some  striking  exam- 
ples with  this  special  point  in  view. 

If  different  orders  of  existing  mammals  were  indeed 
made  by  gradual  modification  of  some  generalized  primal 
form,  then  it  is  evident  that  these  useless  remnants  of 
once  useful  parts  would  be  most  common  in  the  most 
highly   modified    forms.      !N'ow,    of    all    mammals,    the 


1G2    EVIDENCES   OF   THE   TRUTH   OF  EVOLUTION. 

whales  are  perhaps  the  most  modified  or  changed  from 
the  original  mammalian  form  —  so  much  modified,  in 
fact,  that  the  poj^ular  eye  scarcely  recognizes  them  as 
mammals  at  all.  Here,  then,  we  might  exj)ect,  and  do 
indeed  find,  many  examples  : 

1.  The  baleen  whales  have  no  teeth,  and  no  use  for 
them.  They  have  instead  a  wonderful  armature  of 
fringed  whalebone  plates  (baleen),  by  means  of  which 
they  gather  their  food.*  Yet  the  embryo  of  the  whale 
has  a  full  set  of  rudimentary  teeth  deeply  buried  in  the 
jawbone,  and  formed  in  the  usual  way  characteristic  of 
mammalian  teeth — i.  e.,  by  an  infolding  of  the  epithelial 
surface  of  the  gum — but  the  teeth  are  never  cut ;  in  fact, 
they  reach  their  highest  development  in  mid-embryonic 
life,  and  are  again  absorbed.  Why,  then,  this  waste  of 
developmental  energy  ?  AYhy  should  teeth  be  formed 
only  to  be  reabsorbed  without  being  cut  ?  The  only  con- 
ceivable answer  is,  because  the  ancestors  of  the  whale, 
before  the  family  of  whales  was  fairly  established,  had 
teeth  which  were  gradually,  from  generation  to  genera- 
tion, aborted,  because  no  longer  used,  the  baleen  jolates 
having  taken  their  place.  If  whales  were  made  at  once 
out  of  hand  as  we  now  see  them,  is  it  conceivable  that 
these  useless  teeth  would  have  been  given  them  ? 

2.  Again,  many  whales  have  rudimentary  pelvic  bones, 
but  no  hind-limbs.     AVhy  should  there  be  pelvic  bones, 

*  These  baleen  plates  are  not  modifications  of  teeth,  as  might  at  first 
be  supposed,  but  rather  of  the  transverse  gum-ridges  found  on  the  roof 
of  the  mouth  of  many  mammals,  and  conspicuous  in  the  horse. 


PROOFS  FROM  EMBRYOLOGY.       163 

when  the  sole  object  of  these  bones  is  to  act  as  a  basis 
for  hind-limbs  ?  In  some  whales,  for  example  the  right 
whale,  there  are  also  rudiments  of  hind-legs,  but  these 
are  buried  beneath  the  skin  and  flesh,  and  therefore,  of 
course,  wholly  useless.  The  only  explanation  of  these 
facts  is  that  the  ancestors  of  all  the  whales  before  thev 
had  become  whales  were  quadrupeds,  which  afterward 
took  to  the  water,  and  little  by  little  the  hind-legs,  for 
want  of  use,  dwindled  away  to  the  useless  remnants 
which  we  now  find. 

3.  Again,  whales  seem  to  be  hairless,  yet  rudimentary 
hairs  are  found  in  the  skin.  Their  organs  of  smell  are 
rudimentary,  but  made  on  the  pattern  of  those  of  mam- 
mals, not  of  fishes — i.  e.,  they  are  air-smelling,  not 
water-smelling  organs.  From  all  these,  as  well  as  many 
other  facts,  it  is  evident  that  the  whales  descended  in 
early  Tertiary  times  from  some  marsh-loving,  powerful- 
tailed,  short-legged,  scant-haired  quadruped  by  modifica- 
tions gradually  induced  by  increasing  aquatic  habits. 

Examples  of  such  rudimentary  organs  might  be  mul- 
tiplied without  limit.  As  might  be  expected,  some  are 
found  even  in  man.  Such,  for  example,  are  the  muscles 
for  moving  the  ear,  necessary  in  animals  but  useless  in 
man,  and  therefore  rudimentary.  Similarly  useless  in 
man  are  the  scalp-muscle,  used  by  aminals  to  erect  the 
crest  or  bristles  on  the  head,  and  the  skin-muscle  of  the 
neck  and  chest,  used  by  animals  for  shaking  the  skin  of 
those  parts.  Most  persons  have  lost  the  power  of  using 
these.     For  my  part  I  can  use  them  all — ear-muscles. 


16i    EVIDENCES  OF  THE   TRUTH   OF  EVOLUTION. 

scalp-muscle,  skin-muscle — but  they  serve  no  useful  pur- 
pose. 

Again,  and  finally,  in  man  and  many  mammals  we 
find  a  slender,  worm-like  aj^pendage  about  three  inches 
long,  attached  to  the  caecum  of  the  large  intestine. 
Anatomists  and  j)hysiologists,  under  the  influence  of  that 
philosophy  which  maintains  that  every  part  of  the  fear- 
fully and  wonderfully  made  human  frame  was  directly 
contrived  to  subserve  some  useful  purpose,  have  puzzled 
themselves  to  find  the  use  of  this.  It  probably  has  no 
use  ;  on  the  contrary,  it  is  a  continual  source  of  danger. 
If  the  human  body  had  been  made  at  once  out  of  hand, 
it  would  not  have  been  there.  How  came  it,  then  ?  It 
is  the  rudimentary  remnant  of  an  organ — a  greatly  en- 
larged caecum — which  has  served,  and  in  some  mammals 
still  serves,  a  useful  purpose.  All  these  cases  are  sur- 
vivals ;  they  are  organs  which,  like  many  customs  in 
society,  have  outlived  their  usefulness,  but  still  continue 
by  heredity. 

But  why  multiply  examples  ?  All  along  the  track  of 
evolution  organs  become  useless  by  changes  in  the  habits 
of  their  possessors.  They  are  not,  however,  shed  or 
dropped  bodily  at  once.  '  No ;  they  are  retained  hy 
heredity,  but  divmdle  hy  disicse,  more  and  more,  until 
they  pass  away  entirely.  But  even  when  they  are  en- 
tirely gone  in  the  adult,  they  are  often  found  still  lin- 
gering in  the  embryo.  They  are  among  the  most  obvious 
and  convincing  proofs  of  the  origin  of  organic  forms  by 
derivation. 


CHAPTER  VIL 

PEOOFS    FROM    GEOGRAPHICAL   DISTRIBUTION"   OF 

ORGANISMS. 

It  is  well  knowE  that  the  kinds  of  organisms  found 
in  widely-separated  countries  differ  more  or  less  con- 
spicuously. The  traveler  in  Australia  or  in  Africa  finds 
all,  the  traveler  in  Europe  nearly  all,  the  animals  and 
plants  wholly  different  from  those  he  has  been  accus- 
tomed to  see  at  home.  Even  the  visitor  from  the  At- 
lantic to  the  Pacific  coast,  if  he  observes  at  all,  will 
find  nearly  all  organisms  strange  to  him.  The  facts  of 
geographical  diversity  of  organisms  are  so  numerous 
and  complex  that,  at  first  sight,  they  seem  utterly 
lawless.  Only  recently  this  subject  has  been  redeemed 
from  chaos  and  reduced  to  something  like  order  and 
law  by  the  light  thrown  upon  it  by  the  theory  of  evo- 
lution. We  will  give,  in  very  brief  outline,  the  most 
important  facts,  and  then  show  how  they  may  be  ex- 
plained. 

GeograpMcal  Faunas  and  Floras.— The  group  of  ani- 
mals and  plants  inhabiting  any  locality,  whether  pecul- 
iar to  that  locality  or  not,  is   called,  in  popular  Ian- 


166    EVIDENCES  OF  THE   TRUTH   OF  EVOLUTION. 

guage,  its  fauna  and  flora.  But,  in  a  true  scientific 
sense,  a  fauna  and  flora  is  a  natural  group  of  animals 
and  jolants  in  one  place,  differing  more  or  less  conspic- 
uously from  other  groups  in  other  places,  and  separated 
from  them  by  jpliijsico-geograijMcal  boundaries,  or  hy 
joliysical  conditioyis  of  some  hind.  The  members  of 
such  a  group  can  only  exist  in  certain  harmonic  rela- 
tions with  external  conditions,  and  with  one  another. 
These  relations  with  one  another  are  often  comj)lex  and 
nicely  adjusted,  so  that  change  in  one  term  is  propa- 
gated through  the  whole  series  of  terms,  giving  rise 
often  to  the  most  unexpected  results,  until  finally  a 
new  equilibrium  is  established.  Thus,  the  destruction 
of  certain  insectivorous  birds,  in  mere  wanton  sport, 
may  give  rise  to  tlie  multiplication  of  insect  pests,  and 
this  to  the  destruction  of  certain  kinds  of  plants,  and 
this  to  the  diminution  of  certain  herbivores,  and  this 
in  its  turn  to  the  disappearance  of  certain  carnivores. 
It  is  well  known  that  the  introduction  of  rabbits  into 
New  Zealand  and  Australia  has  produced  the  most  un- 
expectedly disastrous  effect  upon  certain  crops,  on  ac- 
count of  the  absence  of  the  fierce  and  active  carnivores 
which  keep  in  check  their  excessive  multiplication  in 
Europe. 

Now,  among  the  physical  conditions  which  limit 
faunas  and  floras,  and  separate  them  from  each  other, 
the  most  important  and  universal  is  temperature. 

Temperature-Regions. — If  we  travel  from  equator  to 
pole,  we  pass  through  mean  temperatures  varying  from 


PPwOOFS  FPwOM  GEOGPvAPHICAL  DISTPJBUTIOX.   1G7 

80°  to  0°o  This  gives  rise  to  a  yery  regular  zonal  ar- 
rangement of  plant-forms  :  1.  We  have  first  a  region 
in  which  palms  and  palm-like  forms  are  abundant  and 
characteristic,  and  which  therefore  mav  be  called  the 
region  of  palms.  It  corresponds  with  the  tropic  zone. 
3.  We  next  have  a  region  in  which  hard-wood  folifer- 
ous  trees  are  most  abundant  and  characteristic ;  first 
mostly  evergreens  and  then  deciduous  trees,  and  there- 
fore may  be  called  the  region  of  hard-wood  forests. 
This  corresponds  with  the  temperate-zone.  3.  Then  we 
find  a  region  characterized  predominantly  by  pines  and. 
pine-like  trees  and  birches,  and  may  be  called  the 
region  of  pines.  This  is  the  sub-Arctic  region.  4. 
Then  a  region  without  trees,  but  only  shrubs  and 
summer  plants.  This  is  the  Arctic  region.  5.  And, 
finally,  an  almost  wholly  plantless  region  of  perpetual 
ice — the  polar  region. 

These  regions  are  determined  wholly  by  temperature, 
and  therefore,  in  going  up  a  mountain-slope  to  snowy 
summits,  we  pass  through  similar  regions  in  smaller 
sj^ace.  For  example,  in  going  from  sea-level  to  the 
summits  of  the  Sierra,  14,000  to  15,000  feet  high,  we 
commence  in  a  region  of  predominantly  hard- wood 
trees  ;  but  at  3,000  feet  the  forests  become  almost 
wholly  coniferous,  at  11,000  to  12,000  feet  the  vegeta- 
tion becomes  shrubby,  and  at  13,000  feet  we  reach 
perpetual  snow. 

We  have  taken  plants  first,  because  these,  being 
fixed   to   the   soil   and   incapable   of  voluntary  seasonal 


168    EVIDENCES   OF  THE   TRUTH   OF  EVOLUTION. 

migrations,  are  more  strictly  and  simply  limited  by 
temperatare — i.  e.,  the  arrangement  of  different  kinds 
in  zones  is  more  simple  and  conspicuous.  But  the 
same  rule  holds  also  for  animals.  In  joassing  from 
equator  to  pole,  animal  kinds  also  change  frequently, 
so  that  there  are  many  temperature-faunas  in  which 
the  animals  are  all  very  different.  In  both  animals 
and  plants,  species,  genera,  families,  etc.,  are  limited 
by  temperature.  These  are  familiar  facts  ;  we  recall 
them  to  the  reader  in  order  that  we  may  base  thereon 
a  clearer  definition  of  these  limits. 

More  Perfect  Definition  of  Regions. — 1.  The  area 
over  which  any  form  spreads  is  called  its  range.  Now, 
the  range  of  a  species  is  more  restricted  than  that  of 
a  genus,  because,  when  a  species  is  limited  by  tempera- 
ture, another  species  of  the  same  genus  may  carry  on 
the  genus.  For  the  same  reason  the  range  of  a  family 
is  usually  greater  than  that  of  a  genus,  and  so  on  for 
higher  classification-groups.  For  example,  pines  range 
on  the  slojDCs  of  the  Sierra  from  about  2,000  feet  to 
11,000  feet,  but  not  the  same  species.  In  ascending, 
we  meet  first  the  nut-pine  {Pinus  Sahiniana),  then  the 
yellow-pine  (P.  j^onderosa),  then  the  sugar-pine  (P. 
Lamlertiana),  then  the  tamarack-pine  (P.  contorta), 
and  last,  the  Pinus  flexiUsy  etc. 

2.  Where  two  contiguous  temperature-regions  come 
in  contact,  there  is  no  sharp  line  between  ;  on  the  con- 
trary, they  shade  gradually,  almost  impercei>tibly,  into 
one  another,  the  ranges  of  species  overlapping  and  in- 


PROOFS  FROM  GEOGRAPHICAL  DISTRIBUTION".    169 


B 


terpenetrating,  and  the  two  species  coexisting  on  the 
borders  of  their  ranges.  This  is  represented  by  the 
diagram  (Fig.  64),  in  which  the  horizontal  lines  repre- 
sent the  north  and  south  ranges 

of  species  of  two  groups,  a  and     ^ 

B,  separated  by  the  dotted  line. 

3.   Species    also     pass     out        

gradually  on  the  borders  of  — 
these  ranges  and  others  come 
in  gradually,  so  far  as  number 
and  vigor  of  individuals  are  concerned.  If  a  a'  and  b  b' 
(Fig.  65)  represent  the  north  and  south  range  of  two 
species,  and  b  a'  their  overlap  or  area  of  coexistence, 
then  the  height  of  the  curves  A  and  b  will  represent  the 

A  B 


Fig.  64. 


Fig.  65. 

number  and   vigor  of  the  individuals  in  different  parts 
of  the  range. 

4.  While,  therefore,  there  is  a  shading  of  contigu- 
ous groups  into  each  other  by  overlap  of  species-ranges  ; 
while  there  is  also  a  gradual  passing  out  of  species  so  far 
as  number  and  vigor  of  individuals  is  concerned,  yet,  in 
specific  characters  we  observe  usually  no  such  gradation. 
Species  seem  to  come  in  on  one  border  with  all  their  spe- 
cific characters  perfect,  remain  substantially  unchanged 
throughout  their  range,  and  pass  out  on  the  other  border, 
still  the  same  species.     In  other  words,  one  species  takes 


170    EVIDENCES   OF  THE   TRUTH   OF  EVOLUTION. 

the  place  of  another,  usually  by  substitution,  not  by 
transmutation.  It  is  as  if  species  had  originated,  no 
matter  how,  each  in  its  own  region,  and  had  spread  in 
all  directions  as  far  as  physical  conditions  and  struggle 
with  other  species  w^ould  allow.  This  important  subject 
will  be  more  fully  discussed  later. 

5.  We  have  thus  far  spoken  of  species  as  limited  by 
temjierature  alone,  but  they  are  limited  also  by  harriers. 
If,  then,  there  be  an  east  and  west  barrier,  such  as  a  high 
mountain-range,  or  a  wide  sea  or  desert,  there  w^ill  be  no 
shading  or  gradation  of  any  kind,  because  the  barrier 
prevents  overlapping,  interpenetration,  and  struggle  on 
the  margins.  For  example  :  The  species  north  and  south 
of  the  Himalayas,  or  north  and  south  of  Sahara,  are 
widely  different.  It  is,  again,  as  if  they  originated  each 
where  we  find  them  and  sjn^ead  as  far  as  they  could,  but 
the  physical  barrier  prevented  mingling  and  shading. 

6.  There  are  temperature-regions  south  as  w^ll  as 
north  of  the  equator.  Now,  although  the  climatic  con- 
ditions are  quite  similar,  the  sj^ecies  of  corresponding 
temperature-regions  north  and  south  are  wholly  differ- 
ent. It  is,  again,  as  if  they  originated  wiiere  we  find 
them,  and  were  kept  separate  by  the  barrier  of  tropical 
heat  between.     If  carried  over,  they  often  do  perfectly 

well. 

Continental  Faunas  and  Floras. 

If  the  land-surfaces  were  continuous  all  around  the 
globe,  there  is  little  doubt  that  each  temperature  region 
with  its  characteristic  species  would  also  be  substantially 


PEOOFS  FROM  GEOGRAPHICAL  DISTRIBUTION.    1^1 


continuous.  There  would,  it  is  true,  be  some  local  varia- 
tions dependent  upon  soil  and  humidity,  etc.,  but  sub- 
stantially the  same  species  would  exist  all  around.  The 
distribution  would  be  almost  wholly  zonal.  But  the  in- 
teryening  oceans  are  complete  barriers  to  continental 
species.  Hence  we  ought  to  expect,  and  do  find,  that  the 
faunas  and  floras  of  different  continents  are  almost  to- 
tally different. 
Each  apparently 
originated  on  its 
own  continent, 
and  did  not 
spread  to  other 
continents,  only 
because  they 
could  not  get 
there.  It  is  ne- 
cessary to  explain 
this  in  more  de- 
tail. 

Fig.  6(j  repre- 
sents a  polar  yiew 
of  the  earth,  showing  the  eastern  and  western  conti- 
nents, and  the  five  temperature  zones  already  described. 
Now,  if  we  examine  the  sj^ecies  in  each  region,  com- 
mencing at  the  pole,  we  find  that  those  of  Nos.  5 
and  4  are  almost  identical  all  around.  The  reason  is 
obvious.  The  continents  come  close  together  there, 
with   ice-connection  if  not  land-connection   all  around. 


Fig.  66. — Polar  projection  of  the  earth.  1,  tropi- 
cal ;  2,  temperate  ;  3,  sub-arctic  ;  4,  arctic ; 
5,  polar  regions. 


172    EVIDENCES   OF   THE   TRUTH   OF  EVOLUTION. 

There  is  but  one  circumpolar  region.  But,  as  soon  as 
we  come  down  to  No.  3  and  No.  2,  the  species  on  the 
two  continents  are  nearly  all  different,  because  there 
is  an  impassable  barrier  between,  either  in  the  form  of 
ocean  or  of  Arctic  cold.  For  example,  the  animals  and 
plants  inhabiting  the  United  States  are  almost  whol- 
ly different  from  those  in  Europe,  not  only  in  species, 
but  even  largely  in  genera  and  to  some  extent  in  families. 
There  are  some  exceptions  to  this  rule,  but  these  are  of 
the  kind  which  prove  the  rule,  or  rather  the  principle  on 
which  the  rule  is  founded.  These  exceptions  are  mainly 
of  three  kinds  :  1.  Introduced  si^ecies. — All  our  weeds, 
many  garden-plants,  and  many  animal  pests  are  of  this 
kind.  They  were  not  found  here  when  America  was 
discovered,  only  because  they  could  not  get  here ;  for, 
when  brought  here,  they  do  so  well  that  they  often  over- 
run the  country  and  dispossess  the  native  species,  as  we 
ourselves  have  done  the  Indians.  2.  Hardy  or  else  wide- 
migrating  species. — Hardy  species  have  wide  range  ;  they 
may  belong  to  No.  4  as  well  as  No.  3.  If  so,  they  range 
down  to  No.  3  on  both  continents.  Migrating  birds,  such 
as  ducks  and  geese,  etc.,  breed  in  summer  in  No.  4,  and 
migrate  southward  in  winter  on  both  continents  from  the 
common  circumpolar  ground.  3.  AJjnne  sjwcies. — It  is 
a  curious  fact  that  species  on  tops  of  snowy  mountains 
in  temperate  regions  of  the  two  continents  are  wonderfully 
similar,  though  so  completely  isolated.  We  are  not  yet 
prepared  to  discuss  this  point.  We  shall  do  so  later. 
Suffice  it  to  say  now  that  it  can  be  completely  explained. 


PROOFS  FEOM  GEOGRAPHICAL  DISTRIBUTION.   173 

In  region  No.  1  the  continental  diversity  is  still 
greater.  Not  only  species  and  genera,  but  whole  fami- 
lies and  even  orders,  are  peculiar  to  each  continent.  The 
great  pachyderms — elephant,  rhinoceros,  hippopotamus — 
are  peculiar  to  the  Eastern  ;  the  edentates — sloths  and 
armadillos — to  the  Western.  The  humming-birds,  those 
gems  of  the  forests,  of  which  there  are  over  four  hun- 
dred species,  and  the  whole  cactus  family,  are  peculiar 
to  America,  while  the  tailless  monkeys  are  equally  char- 
acteristic of  the  Eastern  Continent. 

The  continents  do  not  come  together  again  toward 
the  south,  and,  therefore,  as  might  be  expected,  the 
great  difference  between  the  two  persists  to  the  southern 
points.  The  faunas  of  the  southern  points  of  South 
America,  Africa,  and  Australia  are  very  different. 

Subdivisions  of  Continental  Faunas  and  Floras.— Be- 
sides the  subdivisions  of  continental  faunas,  north  and 
south,  determined  by  temperature  as  already  explained^ 
if  there  be  in  any  continent  an  impassable  barrier  run- 
ning north  and  south,  there  will  be  a  corresponding  dif- 
ference in  the  species  on  the  two  sides,  east  and  west. 
We  give  but  one  example  :  The  North  American  Cordil- 
leras or  Eocky  Mountains,  with  their  high  ranges  and 
desert  plains,  constitute  a  very  great  barrier  between 
the  eastern  and  western  portions  of  the  United  States. 
Heuce,  we  find  an  extraordinary  difference  between  the 
species  inhabiting  California  and  those  found  in  the  east- 
ern portion  of  the  country.  Speaking  generally,  all  the 
species  and  many  of  the  genera  are   peculiar.     The  ex- 


171    EVIDENCES   OF   THE   TRUTH   OF  EVOLUTION. 

ceptions,  too,  are  significaDt.  Leaving  out  introduced 
species,  of  which  there  are  man 3^,  they  are  mostly  strong- 
winged  or  widely-migrating  birds,  such  as  the  turtle- 
dove, the  turkey -buzzard,  the  bald  eagle,  and,  of 
course,  many  water-birds. 

Special  Cases. — If  any  body  of  land  is  widely  sep- 
arated from  all  other  lands  by  deep  seas,  we  invariably 
find  a  corresponding  peculiarity  of  its  species.  Thus, 
the  species  inhabiting  Australia  and  Madagascar  are  per- 
haps the  most  peculiar  in  the  world.  We  do  not  dwell 
further  on  these,  because  we  will  discuss  them  hereafter. 
There  is  a  little  group  of  very  small  islands— the  Gala- 
pagos— about  six  hundred  miles  off  the  western  coast  of 
South  America,  and  surrounded  on  all  sides  by  deep  sea. 
These  islands  are  stocked  with  a  collection  of  curious 
animals  not  found  elsewhere  on  the  surface  of  the  earth  ; 
but  among  them  are  no  mammals  at  all.  We  might 
multiply  examples  without  limit.  Even  the  rivers  empty- 
ing in  the  same  sea  sometimes  have  each*its  peculiar  spe- 
cies of  mussels.  In  the  Altamaha  River  there  are  several 
species  of  unios — such,  for  instance,  as  the  wonderful 
spinous  unio — not  found  elsewhere.  How  came  they 
there  ?  Howsoever  they  may  have  come  there,  they  are 
now  kept  isolated  there  by  barriers  of  land  and  of  salt 
water. 

Many  other  curious  details  will  come  up  in  our  dis- 
cussion of  tlie  origin  of  diversity. 

Marine  Species. — Precisely  the  same  princii^les  apply 
here ;   but   diversity   in   the   case   of   marine   species   is 


PROOFS  FROM  GEOGRAPHICAL  DISTRIBUTION.   175 

perhaps  less  marked,  and  certainly  less  general,  because 
of  the  universal  oceanic  connection.  Open-sea  species 
are  therefore  almost  universal.  But  many  marine  spe- 
cies are  confined  to  shallow  water,  and  therefore  to 
shore-lines.  The  species  on  the  two  shores  of  the  same 
ocean,  or  the  two  coasts  of  the  same  continent,  are  dif- 
ferent, being  isolated  east  and  west  by  barriers  of  deep 
sea  or  of  land,  and  north  and  south  by  temjDerature. 
Also  about  isolated  lands,  like  Australia  and  Madagas- 
car, the  species  are  peculiar. 

Thus,  then,  species,  genera,  etc.,  are  limited  in  every 
direction  ;  north  and  south  by  temperature,  and  in  all  di- 
rections by  barriers,  in  the  form  of  oceans,  deserts,  and 
mountain-chains.  Add  to  these,  peculiar  climates  and 
soils,  and  we  see  that,  from  this  point  of  view,  the 
whole  surface  of  the  earth  may  be  divided  and  sub- 
divided into  regions,  sub-regions,  provinces,  etc.  It 
would  carry  us  too  far  to  explain  the  primary  and 
secondary  divisions  adopted  by  Mr.  Wallace,  and  the 
somewhat  different  ones  suggested  by  Mr.  Allen.  Our 
main  object  is  to  discuss  the  cause  of  this  diversity, 
and  especially  to  show  the  light  shed  upon  it  by  the 
theory  of  evolution.  We  have  only  given  a  sketch  of 
the  facts  sufficient  for  this  purpose. 

Theory  of  tlie  Origin  of  GeogrcqjMcal  Diversity. 

It  will  be  observed  that  all  along  we  have  assumed 

a  sort  of  provisional  theory.      We   have   said   in   every 

case,  it  is  as  if  organic  forms  originated  where  we  find 
9 


176    EVIDENCES   OF   THE    TRUTH   OF   EVOLUTION. 

them,  and  have  gone  thence  wherever  they  could — as 
far  in  every  direction  as  physical  conditions  and  strug- 
gle with  competing  species  would  allow.  This  view 
has  been  formulated  as  the  'theory  of  specific  centers 
of  origin."  There  would  be  less  objection  to  this  as  a 
first  provisional  theory  did  it  not  assume  a  supernatu- 
ral mode  of  origin.  But,  in  the  minds  of  those  who 
hold  it,  it  has  usually  assumed  expressly  or  tacitly  the 
form  of  ^'specific  centers  of  creation,''^  thus  implying 
the  immutability  of  specific  types  and  the  supernatu- 
ralism  of  specific  origin  (page  68).  In  this  latter  or 
usual  form  it  completely  fails  to  account  for  the  facts 
given  above.  For,  if  this  were  the  mode  of  origin, 
each  species  ought  in  every  case  to  be  perfectly  adapt- 
ed to  its  own  environment,  and  to  no  other.  But,  on  the 
contrary,  introduced  species  often  flourish  better  than 
in  their  own  countrv,  and  better  than  the  natives  of 
their  new  homes.  In  the  less  objectionable  form  of 
*^  specific  centers  of  origin,"  without  defining  the  mode 
of  origin,  it  accounts  well  for  many  of  the  more  obvi- 
ous facts  of  geographical  diversity,  as  it  noio  exists,  but 
not  all.  According  to  this  view,  the  amount  of  diver- 
sity ought  to  be  in  strict  proportion  to  the  complete- 
ness of  isolation,  or  impassableness  of  the  separating 
barriers  ;  but  this  is  not  exactly  true.  There  is  another 
element,  not  yet  mentioned,  which  is  just  as  important 
as  impassableness,  but  which  until  recently  has  been 
left  entirely  out  of  account.  This  is  the  element  of 
time — the  amount  of  time  since  the  barrier  was  set  up, 


PROOFS  FROM  GEOGRAPHICAL  DISTRIBUTION.   177 

or  during  which  ifc  has  continued  to  exist.  These  tAvo 
elements,  it  is  true,  are  closely  connected  with  each 
other ;  for,  since  all  changes  in  physical  geography  have 
taken  place  very  slowly — since  barriers  in  the  form  of 
mountain-ranges  and  seas  have  increased  by  slow  pro- 
cess of  growth — it  is  evident  that  impassableness  is,  to 
some  extent,  a  measure  of  time.  But  they  are  by  no 
means  in  strict  proportion.  The  one  or  the  other  may 
predominate. 

Now,  this  time-element  connects  geographical  distri- 
bution with  changes  of  physical  geography  and  climate 
in  geological  times,  and  especially  with  the  latest  of 
these  changes,  viz.,  those  occurring  during  the  Glacial 
ejjocli.  During  that  remarkable  epoch  extraordinary 
changes  of  climate,  from  extreme  Arctic  rigor  to  great 
mildness,  enforced  wide  migrations  of  species  southward 
and  northward  ;  while  concomitant  changes  of  physical 
geography,  by  elevation  of  the  earth's  crust  over  v/ide 
areas,  opened  highways  between  previously-isolated  con- 
tinents, permitting  migrations  in  various  directions,  and 
by  subsequent  depression  again  isolating  the  migrated 
species  in  their  new  homes.  It  is  evident,  then,  that 
the  recognition  of  the  element  of  almost  unlimited 
time  at  once  introduces  into  the  question  of  geographi- 
cal distribution  the  idea  of  evolution.  If  the  study  of 
geographical  distribution,  as  it  noiv  exists,  and  as  a 
part  of  science  of  physical  geography,  gave  rise  natu- 
rally to  the  theory  of  ^'  specific  centers  of  origin,"  the 
study  of  the  same,  in  connection  with  geological  time, 


178    EVIDENCES   OF   THE   TRUTH   OF  EVOLUTION. 

and  as  a  part  of  geological  science,  now  demands  its 
explanation  by  the  theory  of  evolution. 

It  must  be  borne  in  mind,  then,  that  geographical 
diversity  of  organisms  is  not  a  question  of  the  present 
epoch  only.  There  has  been  geographical  diversity  in 
every  previous  geological  epoch  ;  it  is,  therefore,  a  ques- 
tion of  geology  as  well  as  of  biology.  It  is  probable, 
however,  that  diversity  has  increased  with  the  course 
of  geological  times,  and  is  greater  now  than  ever  be- 
fore. In  other  words,  in  the  evolution  of  the  organic 
kingdom,  the  law  of  differentiation  has  prevailed  here, 
as  in  other  dejDartments  of  biology.  A  clear  statement 
of  the  causes  of  the  present  distribution  of  organisms 
must  embrace  also  the  causes  of  geographical  diversity 
generally.  We  give,  therefore,  at  once  a  brief  state- 
ment of  what  seems  to  us  the  most  probable  view,  and 
shall  then  proceed  to  show  how  it  explains  the  present 
distribution. 

Most  Probable  View  of  the  General  Process. — Bear- 
ing in  mind,  then,  this  time-element,  the  phenomena 
of  geographical  diversity  are  best  explained  by  the  fol- 
lowing suppositions  :  1.  A  gradual  progressive  move- 
ment (evolution)  of  the  organic  kingdom,  marching, 
as  it  were,  abreast,  at  equal  rate  along  the  whole  line — 
i.  e.,  in  all  parts  of  the  earth,  and  throughout  all  geo- 
logical times,  under  the  action  of  all  the  forces  or  fac- 
tors, and  following  all  the  laws,  of  evolution  already  ex- 
plained (pages  19  and  73).  If  this  were  all,  there  would 
be  no  geograpliical  diversity,  although  organic  diversity 


PROOFS  FKOM   GEOGRAPHICAL  DISTRIBUTION.   179 

might  be  as  great  as  it  is  now.  There  would  be  dif- 
ferentiatiou  of  forms  and  structure  everywhere,  but  no 
differentiation  of  groups  in  different  localities.  2. 
Under  the  influence  of  different  conditions  in  different 
places,  more  or  less  isolated  from  one  another  by  cli- 
matic or  physical  barriers,  the  onward  movement  (evo- 
lution) of  organic  forms  takes  different  directions  and 
different  rates,  and  gives  rise  to  local  groups,  which 
become  more  and  more  differentiated,  without  limit  as 
time  goes  on.  This  element,  acting  by  itself  through- 
out all  geological  times,  would  ere  this  have  produced 
an  extreme  geographical  diversity,  such  as  does  not  any- 
where exist.  3.  From  time  to  time,  at  long  intervals, 
extensive  changes  of  physical  geography  and  climate, 
produced  by  crust  elevations,  partly  enforce  by  change 
of  temperature,  and  partly  permit  by  opening  of  gate- 
ways, extensive  migrations  and  dispersals  of  species,  by 
which  mingling  and  struggle  for  life  and  final  readjust- 
ment takes  place,  and  extreme  diversity  is  prevented. 
Such  mingling  of  different  faunas  and  floras  on  the  same 
ground,  and  the  severe  struggle  for  life  that  thus  ensues, 
and  the  survival  of  the  fittest  in  many  directions,  are,  as 
already  shown,  among  the  most  powerful  factors  of  evo- 
lution. They  tend  to  increase  organic  diversity,  but  to 
diminish  geographical  diversity.  4.  At  the  close  of  such 
great  periods  of  change  as  indicated  in  the  last,  by  con- 
trary movement  of  the  earth-crust — i.  e.,  subsidence — 
new  barriers  are  set  up  and  new  isolations  are  produced, 
and  the  process   of  divergence    again    commences  and 


180    EVIDEi^CES   OF   THE   TRUTH   OF  EVOLUTION. 

increases   steadily  so   long   as   the   barriers   continue   to 
exist. 

Now.  the  last  of  these  j^eriods  of  great  changes  and 
extensive  migrations,  and  subsequent  isolations,  was  the 
Glacial  epoch.  It  was  this  epoch,  therefore,  which 
mainly  determined  the  present  geographical  distribu- 
tion of  species.  Thus,  the  present  distribution  is  a  key 
to  the  directions  of  the  last  great  migrations,  and  there- 
fore to  the  nature  of  the  changes  in  physical  geogra- 
phy and  climate  which  then  occurred ;  and,  conversely, 
the  character  of  these  changes,  determined  in  other 
ways,  furnishes  the  only  hey  to  the  present  distrihution 
of  species. 

Before  applying  the  foregoing  principles  in  the  ex- 
planation of  special  cases,  it  may  be  well  to  give  a  very 
brief  outline  of  the  condition  of  things  during  the  Gla- 
cial epoch. 

In  America,  during  this  epoch,  by  increasing  cold 
the  southern  margin  of  the  great  northern  ice-sheet 
crept  slowly  southward,  until  it  reached  the  latitude  of 
about  38°  to  40°.  Arctic  sjoecies  were  thus  driven 
southward  slowly,  from  generation  to  generation,  until 
they  occupied  the  whole  of  the  United  States,  as  far 
as  the  shores  of  the  Gulf,  while  temperate  species 
were  forced  still  farther  south,  into  Central  and  South 
America.  This  period  of  extreme  rigor  and  southward 
migration  was  followed  by  a  period  of  great  mildness, 
during  which  the  ice  and  its  accompanying  Arctic  con- 
ditions retreated  northward,  followed  by  Arctic  species. 


PROOFS  FROM  GEOGRAPHICAL  DISTRIBUTION.    181 

More  than  one  advance  and  retreat,  apparently,  oc- 
curred during  this  time.  Again,  during  the  same  time, 
brought  about  by  northern  elevation,  there  was  broader 
connection  than  now  exists  between  North  and  South 
America,  and  free  migrations  between,  in  both  direc- 
tions, enforced  by  extreme  changes  in  temperature. 
Also,  during  this  or  previous  time,  there  were  broad 
connections  between  North  America  and  Asia,  in  the 
region  of  Behring  Strait,  and  between  America  and 
Europe,  in  high-latitude  regions,  and  extensive  migra- 
tions of  faunas  and  floras  between  were  thus  permitted. 
The  necessary  result  of  all  these  migrations  of  species, 
partly  enforced  by  changes  of  climate,  partly  23ermitted 
by  opening  of  gateways  since  closed,  was  exceptionally 
rapid  changes  in  organic  forms.  This  was  the  result  of 
two  causes :  First,  the  severer  pressure  of  a  changing 
physical  environment  ;  and,  second,  a  severer  struggle 
for  life  between  the  natives  and  the  invaders. 

In  Europe,  during  the  same  time  and  from  similar 
causes,  there  were  at  least  three  or  four  different  faunas 
struggling  together  for  mastery  on  the  same  soil.  First, 
there  were  the  Pliocene  indigenes,  who  had,  if  any, 
pre-emption  right  to  the  soil ;  second,  invaders  from 
Arctic  regions,  driven  southward  by  increasing  cold  ; 
third,  invaders  from  Asia,  permitted  by  the  removal 
of  the  old  sea-barrier  which  once  extended  from  the 
Black  Sea  to  the  Arctic,  and  of  whicli  the  Caspian  and 
Aral  are  existing  remnants,  and  thus  opening  a  gateway 
for   migration   which   has   remained    open    ever    since ; 


182    EVIDENCES  OF  THE  TRUTH  OF  EVOLUTION. 

fourth,  invaders  from  Europe  and  Asia  into  Afiica, 
and  sometimes  back  again  into  Euro2:)e,  by  opening  of 
gateways  through  the  Mediterranean,  which  have  been 
since  closed.  One  of  these  highways  was  through  Gib- 
raltar, and  one  from  Italy  to  Africa  through  Sicily. 
As  in  America,  so  here,  in  even  greater  degree,  the 
severe  pressure  of  changing  environment  and  the  severe 
struggle  for  life  produced  rapid  changes  of  organic 
forms.  Many  species  were  destroyed ;  others  saved 
themselves  by  modifications  adapted  more  perfectly  to 
the  changed  conditions.  There  is  little  doubt  that 
man  came  into  Europe  with  the  Asiatic  invasion,  and 
was  one  of  the  principal  agents  of  change,  especially 
in  the  way  of  destruction  of  many  old  forms. 

Such  is  a  very  brief  outline  of  the  last  great  geo- 
logical change  and  its  general  results.  Being  the  last, 
this  one  has  left  the  strongest  and  most  universal  im- 
press on  the  present  geographical  distribution.  But 
similar  changes  by  crust  oscillations,  if  not  also  by 
extreme  changes  of  climate,  have  repeatedly  occurred 
in  geological  times,  and  some  of  the  most  remarkable 
geographical  faunas  and  floras  are  the  result  of  these 
earlier  geological  changes.  AVe  will  now  give  a  few 
examples  illustrating  these  principles: 

1.  Australia  is  undoubtedly  more  peculiar  in  its 
fauna  and  flora  than  any  other  known  country.  Not 
only  are  all  its  species  peculiar,  not  found  elsewhere 
on  the  face  of  the  earth,  but  its  genera,  its  families, 
and  even  many  of  its  orders  of  animals  and  plants,  are 


PROOFS  FROM  GEOGRAPHICAL  DISTRIBUTION.   183 

also  peculiar.  These  facts  are  so  familiar  that  it  is 
unnecessary  to  dwell  on  them.  I  need  only  mention, 
among  plants,  the  whole  of  the  simple-leaved  acacias, 
already  mentioned  on  page  86,  of  which  there  are  so 
many  species,  and  the  whole  family  of  the  eucalyptids, 
of  which  there  are  several  hundred  species.  Among 
animals  I  need  mention  only  the  order  of  monotremes, 
or  egg-laying  mammals,  and  nearly  the  whole  order  of 
marsupials,  or  pouched  animals,  of  which  there  are 
over  two  hundred  species.  On  the  other  hand,  the 
true  typical  mammals  are  entirely  absent,  with  the  ex- 
ception of  a  few  bats  and  a  few  rats,  whicli  have  evi- 
dently been  accidentally  introduced  from  abroad. 

Another  very  noteworthy  fact,  which  must  be  taken 
in  connection  with  the  last,  is  that  Australian  forms 
are  far  less  advanced  in  the  race  of  evolution  than 
those  of  any  other  country — i.  e.,  that  many  old  forms 
which  have  long  ago  become  extinct  elsewhere  are  still 
retained  there.  A  few  examples  will  suffice.  The  mar- 
supials just  mentioned  are  an  old  form  once  universally 
distributed,  but  now  nearly  extinct  everywhere,  except 
in  Australia ;  the  cestracion,  or  Port  Jackson  shark, 
and  the  ceratodus,  are  Palaeozoic  and  Mesozoic  forms 
retained  only  in  Australia. 

What  is  the  explanation  of  these  remarkable  facts  ? 
We  find  the  sufficient  answer  in  the  fact  that  Australia 
has  been  long  isolated  from  all  other  countries.  While 
geographical  changes  in  geological  times  have  mingled 
more  or  less  the  organic  forms  of  other  countries,  and 


184    EVIDEN"CES   OF  THE   TRUTH   OF  EVOLUTION. 

the  sharp  struggle  for  life  has  j)roduced  more  rapid  ad- 
vance and  the  production  of  many  new  and  higher  forms 
better  armed  for  the  battle  of  life,  Australia  has  remained 
isolated  from  competition,  and  therefore  comparatively 
un  progressive. 

Can  we  tell  when  Australia  was  finally  isolated  ?  Ap- 
proximately we  can.  The  class  of  mammals  is  divided 
into  two  groups,  which  differ  widely  from  each  other ; 
so  widely,  that  they  are  called  sub-classes.  These  are 
placental  mammals,  or  true  typical  mammals,  and  non- 
placental  or  rejitilian  mammals.  The  non-placentals  in- 
clude only  the  marsupials  and  the  monotremes  (ornitho- 
rhyncus and  echidna).  The  monotremes  actually  lay 
eggs  and  incubate  them.  In  the  marsupials  the  embryo 
has  no  placental  connection  with  the  mother,  and  is 
born  in  a  very  imperfect  condition,  utterly  unfit  for  in- 
dependent life,  and  placed  in  the  pouch  (marsupium), 
and  permanenthj  attached  there  to  the  teat  until  it  is 
capable  of  independent  life  ;  after  which  only  it  volunta- 
rily nurses  like  other  new-borns.  In  other  words,  the 
gestation  commenced  in  the  womb  is  completed  in  the 
pouch.  The  uterine  gestation  in  the  opossum  is  only 
seventeen  days,  while  the  marsupial  gestation  is  about 
two  and  a  half  months.  In  a  kangaroo  seven  feet  high 
in  sitting  position  the  embrvo  at  birth  is  only  one  inch 
long — a  pink,  hairless,  almost  amorphous  mass.  The 
monotremes  are  pure  oviparous  animals,  like  birds  and 
reptiles.  The  marsupials  might  well  be  called  semi- 
oviparous.     In  pure  egg-layers  the  whole  embryonic  de- 


PROOFS  FROM  GEOGRAPHICAL  DISTRIBUTION.   185 

velopment  is  outside  of  the  body  ;  in  pure  young-bearers 
the  whole  is  within  the  body  ;  in  marsupials  it  is  paiUy 
within  and  partly  without.  Now — 1.  The  monotremes 
are  found  nowhere  but  in  Australia  and  the  neighbor- 
ing New  Guinea.  2.  The  marsupials  are  also  all  con- 
fined to  the  Australian  region,  except  a  few  oppossums 
in  America.  3.  There  are  some  two  hundred  and  thir- 
ty species  of  non-placentals  in  the  Australian  region. 
4.  As  already  said,  there  are  no  true  mammals  at  all  in 
Australia,  except  a  few  bats  and  rats  which  have  come 
accidentally  from  abroad.  5.  But  non-placentals  existed 
abundantly  in  Mesozoic  times  everyivhere,  both  in  Eu- 
rop-Asia  and  in  America,  while  true  mammals  did  not 
appear  at  all  on  the  surface  of  the  earth  until  the  Ter- 
tiary, when  they  almost  immediately  became  very  abun- 
dant everywhere,  except  in  Australia.  Evidently,  there- 
fore, Australia  was  isolated  before  the  Tertiary.  The 
enormous  diiference  between  its  fauna  and  flora  and 
those  of  other  countries  is  due  to  at  least  three  things  : 
1.  So  long  an  isolation  necessarily  produced  great  diver- 
gence of  forms.  This  alone,  however,  would  not  affect 
the  grade  of  organization.  2.  Saved  from  wide  migra- 
tions, and  especially  invasions  from  Eurasia,  the  great 
field  of  competitive  struggle,  it  was  left  far  behind  in 
the  race  of  evolution.  Hence  many  of  its  forms  are  ar- 
chaic ;  its  mammalian  fauna,  for  Instance,  is  still  m  the 
Mesozoic  stage.  3.  Its  distance  from  other  large  conti- 
nents is  so  great  that  accidental  colonization  has  been 
very  slight,  only  extending  to  a  few  bats  and  a  few  rats. 


186    EVIDENCES   OF   THE   TRUTH   OF  EVOLUTION. 

I  stop  a  moment  to  insist  on  the  effect  of  competitive 
struggle  in  developing  organic  forms  strong  for  the  battle 
of  life.  Of  all  the  continents,  Eurasia  has  been  the  scene 
of  most  frequent  geological  changes,  and  therefore  the 
arena  of  fiercest  competitive  struggle  through  wide  and 
frequent  migrations.  Eurasian  species,  therefore,  are 
the  strongest  of  all.  They  have  conquered  wherever 
they  have  gone.  Species  in  isolated  regions  are  usually 
the  weakest.  The  great  moas  and  the  dodo  could  not 
have  continued  to  exist  unless  protected  in  a  sort  of 
bomb-proof.  Kangaroos  would  now  be  quickly  extermi- 
nated by  the  introduction  of  fierce  Eurasian  carnivores. 

2.  Africa. — The  fauna  of  that  part  of  Africa  north 
of  Sahara  is  essentially  Mediterranean — i.  e.,  a  sub-group 
of  the  Eurasian.  Sahara,  rather  than  the  Mediterranean 
Sea,  is  the  true  intercontinental  barrier.  The  true  Afri- 
can region,  tlierefore,  is  south  of  Sahara.  Now,  accord- 
ing to  Mr.  Wallace,  whom  I  mainly  follow  here,  the  true 
African  mammalian  fauna  consists  of  two  very  different 
groups  of  animals.  The  one  is  a  group  of  very  small, 
curious  animals,  mostly  low  forms  of  insectivores  and 
lemurs,  very  peculiar  to  this  region,  though  more  resem- 
bling those  of  Madagascar  than  of  any  other  region  ;  the 
other  is  a  group  of  large  and  powerful  animals  which 
dominate  the  region.  These  latter  are  similar  to,  though 
not  identical  with,  those  which  inhabited  Eurasia  in  Pli- 
ocene times.  The  great  carnivores,  pachyderms,  and  ru- 
minants of  the  region  are  examples  of  this  group.  Now, 
the  explanation  of  these  facts  is  as  follows  :  The  indige- 


PROOFS  FROM  GEOGRAPHICAL  DISTRIBUTION.   18T 

nes  of  Africa  are  the  animals  of  the  first  group.  Africa, 
in  Tertiary  times,  was  isolated  from  the  great  field  of 
combat,  Eurasia,  and  therefore  its  animals  were  small,  of 
low  grade,  and  peculiar.  During  later  Tertiary  (Plio- 
cene) times,  then,  Africa  was  inhabited  by  animals  of  the 
first  group,  while  Eurasia  was  dominated  by  animals  of 
the  second  group.  These  two  groups  were  then  sepa- 
rated by  the  Desert  of  Sahara,  or  else  by  a  sea  in  that  re- 
gion. Some  time  during  the  Glacial  epoch  geographical 
changes  removed  this  barrier,  and  climatic  changes  drove 
the  Eurasian  animals  southward  into  Africa,  where,  find- 
ing congenial  climate,  they  took  possession  of  the  conti- 
nent, dominating  the  feebler  natives.  Subsequently  they 
were  isolated  there  by  the  formation  of  the  desert,  and 
the  process  of  divergence  commenced,  and  has  gone  on 
to  the  formation  of  many  new  forms.  Meanwhile  the 
change,  partly  by  extinction  and  partly  by  modification, 
has  gone  on  still  more  rapidly  in  Eurasia,  but  in  a  dif- 
ferent direction.  Hence,  Africa  is  regarded  as  one  of  the 
primary  faunal  regions. 

3.  Madagascar.  —  This,  next  to  the  Australian,  is 
probably  the  most  peculiar  faunal  region  known.  There 
is  probably  not  a  single  mammalian  species  found  there 
which  is  known  to  occur  anywhere  else.  It  is  remarkable 
also  as  the  principal  home  of  that  strange,  generalized, 
ancient  form  of  monkeys — the  lemurs.  And  yet  its  ani- 
mals, though  very  different,  have  a  distant  resemblance  to 
those  of  Africa ;  not,  however,  to  the  present  dominant 
type,  but  to  those  we  have  called  the  indigenes.     Not 


188    EVIDENCES   OF  THE   TRUTH   OF  EVOLUTION.      ' 

one  of  the  northern  invaders  is  found  there.  The  ob- 
vious conclusion  from  these  facts  is,  that  Madao-ascar 
was  formerly  united  with  Africa,  and  both  were  occupied 
by  the  same  mammalian  fauna  (which  may  be  called  Af- 
rican indigenes,  although  they  were  considerably  differ- 
ent from  their  descendants  of  the  jDresent  day),  but  be- 
came separated  before  the  northern  invasion.  The  effect 
of  this  invasion  was  to  hasten  the  steps  of  change  in  the  in- 
digenous fauna  of  Africa,  partly  by  extermination,  partly 
by  modification,  while  the  isolated  portion  in  Madagascar 
went  on  at  the  usual  slow  rate  of  change  in  isolated  re- 
gions. The  time  since  the  separation  (which  was  cer- 
tainly during  the  Tertiary  i^eriod)  has  been  sufficiently 
long  to  produce  very  great  divergence  in  both,  but  espe- 
daily  in  the  African  indigenes.  In  the  fauna  of  Mada- 
gascar, therefore,  we  have  a  nearer  approach  to  the  origi- 
nal fauna  of  both.  On  account  of  this  long  isolation,  we 
have  here  many  ancient  types  which  are  extinct  else- 
where. The  lemurs  are  such  an  ancient  type.  These  are 
a  wonderfully-generalized  type  of  monkeys — a  connect- 
ing link  between  monkeys  and  other  mammals,  especially 
insectivores.  As  might  be  supposed,  from  the  law  of  dif- 
ferentiation, already  explained  (page  11),  they  are  the 
earliest  form,  the  progenitors,  of  monkeys.  In  fact,  in 
early  Tertiary  times,  they  were  found  not  only  in  Africa 
and  Madagascar,  but  all  over  the  earth,  as  the  only  rep- 
resentatives of  the  monkey  family.  The  true  monkeys 
were  not  introduced  until  the  mid-Tertiary.  In  Eura- 
sia and   in   America  (which  at  that  time   was  probably 


PROOFS  FROM  GEOGRAPHICAL  DISTRIBUTION.   189 

connected  with  Eurasia)  wide  migrations  and  frequent 
conflicts  of  faunas  produced  comparatively  rapid  evolu- 
tion of  new  and  higher  forms,  while  in  isolated  Africa 
old  types  continued  until  the  invasion.  Madagascar  was 
spared  this  invasion,  and  therefore  old  types  are  still  pre- 
served there.  At  present,  at  least  three  quarters  of  all 
lemurs  are  confined  to  Madagascar,  although  a  few  spe- 
cies are  still  found  in  Africa  and  in  the  great  East  Indian 
islands. 

4.  Island-Life. — Mr.  Wallace  has  divided  islands  into 
two  kinds,  continental  and  oceanic  islands.  The  division 
is  undoubtedly  a  good  one,  although  we  may  not  always 
be  able  to  refer  an  example  with  certainty  to  the  one  or 
the  other  class.  Continental  islands  are  those  on  the  bor- 
ders of  continents,  and  separated  from  the  latter  only  by 
slialloiu  ivater.  Oceanic  islands  are  those,  usually  very 
small,  found  in  the  midst  of  the  ocean,  with  abyssal 
depth  all  about.  Continental  islands  may  be  regarded  as 
appendages  to  the  neighboring  continent — as  outliers  of 
continents  separated  by  submergence,  and  have,  in  fact, 
been  thus  formed.  Oceanic  islands  have  been  formed 
geologically  recently  by  volcanic  action  building  up  from 
the  sea-bottom.  Continental  islands  have  a  continental 
structure — i.  e.,  they  are  composed  of  stratified  as  well 
as  of  igneous  rocks.  Their  structure  is  a  record  of 
geological  history,  like  that  of  the  neighboring  continent. 
Oceanic  islands  are  composed  wholly  of  volcanic  rocks  ; 
or,  if  there  be  any  stratified  rocks,  these  are  only  of  the 
most  recent  date.     As  examples  of  continental  islands  we 


190  EVIDENCES   OF  THE   TRUTH   OF   EVOLUTION". 

have  New  Zealand  as  an  appendage  of  Australia,  the 
great  East  Indian  (Borneo,  Java,  Sumatra,  etc.)  and  the 
Japanese  Islands,  etc.,  as  appendages  of  Asia  ;  the  British 
Islands,  appendages  of  Europe  ;  the  West  Indian  Islands, 
appendages  of  America ;  Madagascar,  an  appendage  of 
Africa,  etc.,  etc.  As  examples  of  oceanic  islands  we 
have  the  Azores  and  Bermudas  in  the  Atlantic,  and  the 
Polynesian  islands  in  mid-Pacific. 

a.  Continental  Islands. — Now,  the  fauna  of  conti- 
nental islands,  as  might  be  expected  from  the  mode  of 
origin  of  these  islands,  is  similar  to,  though  not  identical 
with,  that  of  the  neighboring  continent ;  the  amount  of 
difference  being  in  proportion  to  the  length  of  time  since 
they  were  separated  and  the  width  of  the  separatio7i. 
Madagascar,  for  example,  has  been  long  separated  from 
its  parent  continent,  and  by  a  wide  and  deep  channel. 
Its  fauna,  therefore,  differs  greatly  from  that  of  Africa, 
although  resembling  it  more  than  that  of  any  other 
country.  The  separation  of  JVciv  Zealand  from  Aus- 
tralia has  been  not  quite  so  long,  and  the  divergence, 
therefore,  is  not  so  great.  These  two  will  be  sufficient 
illustrative  examples  of  long  separation,  and  therefore 
of  great  differentiation  of  forms. 

On  the  other  hand,  the  British  Isles  are  an  excellent 
example  of  comparatively  recent  separation.  These  isles 
have  probably  been  several  times  united  and  separated 
from  Europe,  but  we  are  here  concerned  only  with  the 
more  recent.  They  are  now  separated  from  the  conti- 
nent and  from  one  another  only  by  shallow  seas.     An 


PROOFS  FROM  GEOGRAPHICAL  DISTRIBUTION".   191 

elevation  of  less  than  six  hundred  feet — geologically  a 
yerv  small  chaiis^e — would  bare  the  bottoms  of  the  Irish 
and  English  Channels  and  the  North  Sea,  and  connect 


Fig.  67. — Map  of  outline  of  coast  of  Western  Europe,  if  elevated  600 

feet  (after  Ljcll). 


192  EVIDENCES   OF   THE   TRUTH   OF  EVOLUTION". 

these  islands  with  one  another  and  with  the  continent 
(Fig.  67).  Now,  it  is  well  known  that  there  were  dur- 
ing the  Glacial  epoch,  and  subsequently,  several  oscilla- 
tions of  level  sufficient  to  connect  and  separate  these 
islands.  In  the  mid-Glacial  ei:»och  the  British  Islands, 
by  submergence,  were  nearly  obliterated,  being  reduced 
to  an  archipelago  of  small  islets  representing  the  high 
mountains  of  Wales  and  Scotland.  The  Pliocene  fauna 
and  flora  were,  therefore,  largely  exterminated.  During 
the  close  of  that  epoch  they  were  elevated  above  the 
present  condition  and  broadly  connected  with  the  con- 
tinent (Fig.  67),  and  the  newly-exposed  land  was  taken 
possession  of  by  European  species,  man  among  the  num- 
ber. Still  later — i.  e.,  at  the  beginning  of  the  present 
epoch — the  islands  by  subsidence  were  again  separated, 
but  not  widely,  from  the  continent.  This  is  the  condi- 
tion now.  What,  then,  was  the  result  ?  1.  The  fauna 
and  flora  of  the  British  Isles  are  substantiallv  the  same, 
but  less  rich  in  species  than  that  of  Continental  Europe, 
some  of  the  European  species  being  wanting.  This  shows 
that  the  last  connection  was  not  a  long  one  ;  the  coloni- 
zation had  not  been  completed  before  re-isolation.  2. 
This  poverty  of  species  is  more  conspicuous  in  Ireland, 
because  colonization  is  progressive  in  space  as  well  as  in 
time.  Some  species  had  not  reached  so  far  when  Ireland 
was  re-isolated  from  England.  The  conspicuous  absence 
of  snakes,  for  example,  is  thus  accounted  for.  There  is, 
we  all  know,  another  theory  to  account  for  this,  but  we 
prefer  the  natural  one.     3.  The  difference  between  Brit- 


PROOFS  FROM  GEOGRAPHICAL  DISTRIBUTION.   193 

isli  and  European  fauna  and  flora  is  very  small,  it  is 
true,  but  there  is  some  difference,  val'ietal  if  not  specific. 
The  reason  is,  that  the  time  since  separation  is  too  small 
to  produce  much  divergence,  and  the  width  of  the  exist- 
ing barriers  not  great  enough  to  prevent  colonization  by 
accidental  causes. 

The  continental  islands  of  the  southern  coast  of 
Asia  are  good  examples  of  an  intermediate  condition  as 
to  the  length  of  time  since  separation,  and  of  the 
consequent  degree  of  differentiation  of  the  faunas  and 
floras. 

Coast-Islands  of  California. — We  give  one  more  exam- 
ple, and  dwell  upon  it  a  little,  because  it  occurs  on  our 
own  coast. 

The  recent  studies  of  Mr.  E.  L.  Greene  on  the  flora 
of  the  islands  off  the  coast  of  California  have  brought  to 
lioht  some  facts  which  are  an  admirable  illustration  of 
the  principles  laid  down  above. 

On  looking  at  a  good  map  of  California,  any  one  will 
observe  eight  or  ten  islands,  some  of  them  of  consider- 
able size,  strung  along  the  coast  from  Point  Conception 
southward,  and  separated  from  the  mainland  by  a  sound 
twenty  to  thirty  miles  wide.  They  are  in  structure  true 
continental  islands — outliers  of  the  mainland  separated 
by  a  subsidence  of  a  few  hundred  feet.  Moreover,  the 
date  of  their  separation  is  known.  They  were  certainly 
connected  with  the  mainland  during  the  later  Pliocene 
and  early  Quaternary,  for  bones  of  the  mammoth,  char- 
acteristic  of    that    time,  have    been   found  on   one   of 


194  EYIDEXCES  OF  THE   TRUTH   OF  EVOLUTION. 

them.*     They  were  therefore  separated  during  the  Gla- 
cial epoch. 

The  main  i^eculiarities  of  the  flora  of  these  islands  are 
the  following  : 

1.  Out  of  nearly  three  hundred  species  of  j^lants  gath- 
ered by  Mr.  Greene,  about  fifty  are  wholly  peculiar  to 
these  islands.  2.  Of  the  remaining  two  hundred  and  fifty 
species,  nearly  all  are  distinctively  Calif ornian.  In  other 
words,  the  distinctively  Californian  forms  are  very  abun- 
dant, while  the  common  American  forms  are  rare — i.  e., 
the  island  flora  is  distinctively  Californian,  with  many 
peculiar  species  added. 

I  explain  these  facts  as  follows  :  The  whole  coast- 
region  of  California  is  geologically  very  recent,  having 
emerged  from  the  sea  as  late  as  the  beginning  of  the  Pli- 
ocene epoch.  As  soon  as  emerged  it  was  of  course  colo- 
nized from  adjacent  parts.  Since  that  time  its  peculiar 
flora  has  been  formed  by  gradual  modification.  The  en- 
vironment has  been  sufficiently  joeculiar,  the  isolation 
sufficiently  complete,  and  the  time  sufficiently  long,  to 
make  a  very  distinct  group  of  organisms.  It  is  one  of 
Mr.  Wallace's  primary  divisions  of  the  Ne-arctic  region. 

During  late  Pliocene  and  early  Quaternary  times,  as 
already  said,  the  islands  were  still  a  part  of  the  mainland, 
and  the  whole  was  occupied  by  the  same  species,  viz., 
the  distinctively  Californian  species  now  found  in  both, 
together,  as  I  suppose,  with  the  peculiar  island  species. 

*  "Proceedings  of  the  California  Academy  of  Science,"  vol.  v,  p.  152, 
1873. 


PROOFS  FROM  GEOGRAPHICAL  DISTRIBUTION.   195 

During  the  oscillations  of  the  glacial  times  the  islands 
were  separated  by  subsidence  of  the  continental  margin. 
Simultaneously  with  this  subsidence,  or  subsequently 
thereto,  came  the  invasion  of  northern  species,  driven 
southward  by  glacial  cold.  Then  came  the  mingling  of 
invaders  with  natives,  the  struggle  for  mastery,  the  ex- 
termination of  many  forms — viz.,  the  peculiar  island  spe- 
cies— and  the  slight  modification  of  others,  and  the  final 
result  is  the  California  flora  of  to-day.  But  the  island 
flora  was  spared  this  invasion  by  isolation.  Therefore 
the  invading  species  are  mostly  wanting,  the  distinctive 
island  species  were  saved,  and  the  result  is  the  island  flora 
of  to-day.  The  island  flora,  therefore,  somewhat  nearly 
represents  the  Pliocene  indigenes  of  both. 

It  will  be  observed  that  this  case  is  somewhat  like 
that  of  Madagascar,  but  with  a  characteristic  difference. 
In  the  case  of  Madagascar,  the  separation  has  been  long. 
The  extreme  peculiarity  of  its  fauna  is  the  result  partly 
of  progressive  divergence  and  partly  of  many  forms  saved 
by  isolation.  In  the  case  of  the  coast-islands  of  Califor- 
nia, the  time  has  not  been  long  enough  for  any  great 
divergence  by  modification.  The  peculiarity  of  its  spe- 
cies is  due  almost  wholly  to  species  saved  by  isolation.* 

b.  Oceanic  Islands. — We  have  seen  that  faunas  and 
floras  of  continental  islands  are  somewhat  similar  to  those 
of  the  neighboring  continent,  though  with  varying  degrees 

*  For  fuller  discussion  of  this  subject,  see  "  Bulletin  of  the  Califor- 
nia Academy  of  Science,"  No.  8,  1887,  and  "American  Journal  of  Sci- 
ence," for  Dec,  1887. 


196   EVIDENCES   OF   THE   TRUTH   OF  EVOLUTION. 

of  difference— the  amount  of  difference,  or  divergence  by 
evolution,  being  in  proportion  to  the  amount  of  time  and 
the  impassableness  of  the  separating  barriers.  But  ocean- 
ic islands  have  never  been  connected  with  any  continent. 
They  are  new  land  formed  in  the  midst  of  the  ocean  by 
volcanic  action.  When  they  first  appeared  they  were,  of 
course,  without  inhabitants  of  any  kind,  animal  or  vege- 
tal. How  were  they  peopled  ?  We  answer  by  ivaifs 
from  here  and  there  —  by  castaivays  from  other  lands. 
The  dominance  of  particular  kinds  will  depend  on  the 
direction  of  winds  and  currents,  bringing  from  some 
lands  more  than  others,  and  upon  the  kinds  of  animals 
or  seeds  of  plants  most  liable  to  be  successfully  carried 
across  wide  seas.  Their  faunas  and  floras,  therefore,  are 
characterized  by  a  mixture  of  species  resembling,  though 
not  usually  identical  with,  those  of  various  lands,  with  a 
predominance  of  those  of  some  one  land,  and  by  the 
singular  and  complete  absence  of  mammals  and  amphib- 
ians, these  being  unlikely  to  be  transj)orted  by  floating 
timber,  as  are  small  reptiles  and  insects,  etc.  Among 
mammals,  however,  there  is  a  significant  exception  in 
favor  of  bats,  the  reason  being  both  their  power  of  flight 
and  their  habit  of  concealment  in  hollow  trees,  etc.  To 
this  explanation,  however,  we  must  add  that  divergence 
by  isolation  will  meanwhile  go  on  in  proportion  to  time. 
The  Azores,  for  example,  have  been  peopled  from  Eu- 
rope, Africa,  and  America,  but  mostly  from  Europe,  on 
account  of  the  prevailing  winds  and  currents  being  favor- 
able  to   colonization   from   that   direction.      There   are 


PROOFS  FROM  GEOGRAPHICAL  DISTRIBUTION.   197 

many  curious  peculiarities  in  the  species,  howeyer,  be- 
cause colonization  is  very  slow,  and  divergent  variation 
has  been  going  on  pari  passu.  The  Bermudas,  on  the 
other  hand,  have  been  colonized  mainly  from  America, 
because  of  the  current  of  the  Gulf  Stream. 

These  few  examples  are  sufficient  for  our  purpose, 
which  is  only  to  illustrate  the  causes  of  geographical  dis- 
tribution. If  any  one  desires  to  pursue  this  interesting 
subject,  we  would  refer  him  to  that  most  fascinating 
book,  Mr.  Wallace's  ^Island-Life." 

5.  Alpine  Species. — These  afford  an  admirable  illus- 
tration of  the  fact  that  in  isolated  faunas  and  floras  the 
amount  of  difference  is  proportioned  not  only  to  the 
comj^leteness  of  isolation,  but  also  and  mainly  to  the 
time  of  isolation. 

It  is  well  known  that  Alpine  species — i.  e.,  those  spe- 
cies inhabiting  the  region  bordering  the  joerpetual  snow 
of  lofty  mountains — are  very  siuiilar  to  one  another,  even 
in  the  most  distant  localities,  where  their  isolation  from 
one  another  is  as  complete  as  possible  ;  as,  for  example,  in 
the  high  Alps  of  Europe,  the  high  mountains  of  Colo- 
rado and  California.  Why  is  this  ?  We  find  the  key  to 
this  mystery  in  the  additional  fact  that  they  are  similar 
also  to  Arctic  species.  A  somewhat  full  explanation  is 
here  necessary. 

During  Miocene  times,  magnolias  and  taxodiums  (bald 
cypress),  like  those  in  forests  and  swamps  of  Carolina 
and  Louisiana,  and  sequoias  and  libocedrus  like  those 
now   in   California,   and    many  other   temperate  -  region 


198   EVIDENCES   OF   THE   TRUTH   OF  EVOLUTION. 

forms  of  plants,  grew  abundantly  in  Greenland,  and  north- 
ward certainly  to  75°  north  latitude.  At  that  time  there 
could  not  have  been  any  perpetual  polar  ice,  and  there- 
fore no  Arctic  species,  unless  on  high  mountains  in  polar 
regions.  In  Pliocene  times  perpetual  polar  ice,  and  there- 
fore Arctic  species,  probably  commenced  to  appear.  As 
the  cold  of  the  Glacial  epoch  came  on  and  increased  in 
severity,  the  j)olar  ice  extended  southward  as  a  general 
ice-sheet,  until  it  reached  in  America  40°  and  in  Europe 
about  50°  north  latitude.  In  the  United  States  its  mar- 
gin can  be  traced  as  a  distinct  moraine  through  Long 
Island,  middle  ^ew  Jersey,  middle  Penns3^1vania ;  thence, 
less  distinctly,  following  the  Ohio  River,  crossing  the  Mis- 
sissippi ;  thence  following  the  Missouri,  on  its  south  side, 
into  Montana.  By  the  increasing  cold,  Arctic  species 
were  driven  slowly  southward,  generation  after  genera- 
tion, until  they  occupied  the  whole  of  the  United  States 
to  the  Gulf,  and  the  whole  of  Europe  to  the  Mediterra- 
nean. As  these  species  on  the  two  continents  came  from 
a  common  home  in  polar  regions,  they  were  similar  to 
one  another,  except  in  so  far  as  some  slight  divergent 
modification  may  have  been  2:)roduced  during  their  south- 
ward travel.  When  the  glacial  rigor  declined,  and  the 
ice-sheet  gradually  retreated  to  its  present  position,  Arc- 
tic species,  following  the  snow-edge,  went  also  north- 
ward, on  both  continents,  to  their  present  home  in  jiolar 
regions.  But  there  was  an  alternative  vray  of  migration 
left  open  which  was  embraced  by  certain  plants  and  in- 
sects.    While  on  both  continents  most  individuals  went 


PROOFS  FROM  GEOGRAPHICAL  DISTRIBUTION.   199 

northward^  some  of  them  went  upward,  following  the  snow- 
edge  into  high  mountains,  and  were  left  stranded  there. 
Thus  it  has  come  to  pass  that  the  plants  and  insects  of  high 
mountains  in  temperate  regions  of  different  continents, 
though  so  widely  separated  and  impassably  isolated,  are 
extremely  similar  to  one  another.  But,  though  similar, 
they  are  rarely  identical.  The  time  has  been  long  enough 
for  some  but  not  very  great  divergent  modification.  It 
is  impossible  to  conceive  a  more  beautiful  illustration  of 
the  principles  we  have  been  trying  to  enforce. 

Thus,  then,  undoubtedly  all  the  ^^henomena  of  geo- 
graphical distribution  of  sj^ecies  are  most  rationally 
explained  on  the  principle  of  slow  evolution  -  changes, 
different  in  different  places,  and  increasing  with  the  time 
of  isolation  and  its  completeness. 

Objection. — The  only  objection  which  can  be  raised 
against  this  view  is  the  manner  in  which  contiguous  geo- 
graphical faunas  and  floras  pass  into  one  another  when 
they  are  limited  not  hy  harriers  hut  hy  temperature.  In 
passing  from  equator  to  poles,  over  continuous  land, 
we  of  course  pass  through  many  successive  faunas  and 
floras,  limited  wholly  or  mainly  by  temperature.  Now,  if 
species  are  indeed  indefinitely  modifiable,  then  on  the  bor- 
ders of  contiguous  faunas  or  floras,  where  one  species  dis- 
appears and  another  closely  allied  but  adapted  to  a  colder 
temperature  takes  its  place,  the  one  species  (say  the  anti- 
evolutionists)  ought  to  be  gradually  transmuted  into  the 

other,  so  that  all  the  gradations  may  be  traced.    But  this 
10 


200    EVIDENCES   OF   THE  TRUTH   OF  EVOLUTION. 

is  certainly  not  usually  the  fact.  On  the  contrary,  a 
species  may  indeed  pass  out  gradually,  and  another  come 
in  gradually,  so  far  as  numher  and  vigor  of  individuals 
are  coyicerned ;  but,  in  specific  character,  they  may 
be  said,  usually  at  least,  to  come  in  suddenly,  with  all 
their  characters  perfect,  remain  unchanged  throughout 
their  whole  range,  and  pass  out  suddenly  at  its  borders. 
Another  species  takes  its  place,  overlapjoing  in  range  and 
coexisting  on  the  borders  of  both  ;  this  also  continues 
unchanged,  as  far  as  it  goes,  and  so  on.  The  change 
from  one  fauna  to  another  is  apparently  not  by  transmu- 
tation of  one  species  into  another  by  gradations,  but  by 
suhstitution  of  one  perfect  species  for  another  perfect 
species.  As  a  broad  general  statement,  the  condition  of 
things  is  precisely  such  as  would  be  the  case  if  specific 
types  were  substantially  immutable  by  physical  con- 
ditions, but  were  originated  in  some  inscrutable  way 
(created)  in  the  regions  where  we  now  find  them,  and 
have  spread  in  every  direction  as  far  as  physical  condi- 
tions and  struggle  with  other  species  w^ould  allow  them — 
their  ranges  therefore  interi^enetrating  and  overlapping 
one  another  on  their  borders. 

Two  characteristic  examples  will  make  our  meaning 
clear.  There  is  not  a  more  characteristic  tree  known 
than  the  sweet-gum,  or  liquidambar.  This  tree  grows 
from  the  borders  of  Florida  to  the  shores  of  the  Great 
Lakes.  It  may  indeed  be  most  numerous  and  vigorous 
somewhere  in  the  middle  region,  and  may  die  out  grad- 
ually in  number  and  vigor  of  individuals  on  the  borders 


PROOFS  FROM  GEOGRAPHICAL  DISTRIBUTION.   201 

of  its  range,  but  in  specific  character  it  is  substantially 
the  same  throughout,  easily  recognizable  by  its  dense 
wood,  its  winged  bark,  its  five-starred  leaf,  its  spinous 
burr,  and  its  fragrant  gum.  Physical  conditions  may 
diminish  its  number  and  vigor,  and  limit  its  extension, 
but  seem  powerless  to  essentially  modify  its  specific  char- 
acter. It  seems  to  give  up  its  life  rather  than  change 
its  nature. 

Another  striking  example  :  The  sequoias  (redwood 
and  big-tree)  are  entirely  confined  to  California,  and 
there  are  only  two  species  now  existing,  viz.,  the  redwood 
(S.  sempervirens)  of  the  Coast  Ranges,  and  the  big-tree 
{S.  gigantea)  of  the  Sierra  Nevada.  Doubtless  they  are 
most  numerous  and  vigorous  somewhere  in  the  middle 
of  their  range,  and  die  out  gradually  in  number  and 
vigor  on  the  borders  north  and  south,  being  replaced 
there  by  other  genera  better  adapted  to  the  physical 
conditions  ;  but  in  specific  character  they  remain  essen- 
tially unchanged  throughout.  They  are  everywhere 
the  same — easily  recognizable  by  wood,  bark,  leaf,  and 
burr.  Both  in  this  case,  and  in  the  previous  one  of 
the  sweet-gum,  it  is  as  if  they  were  created  perfect  in 
their  present  localities,  and  have  spread  in  all  directions 
as  far  as  physical  conditions  and  the  struggle  with  other 
competing  species  would  allow  ;  but  physical  conditions 
seem  powerless  to  change  them  into  any  other  species 
by  ada^Dtive  modification. 

Answer. — We  have,  we  believe,  stated  the  objection 
fairly.      The  answer  is,  that  the  elements  of  time  and 


202  EVIDENCES   OF  THE    TRUTH  OF  EVOLUTION 

of  migrations  have  not  been  taken  into  the  account.  In 
fact,  this  objection  was  conceived  and  formulated  before 
the  idea  of  geological  time  was  fully  assimilated  by  the 
human  mind,  and  our  theories  of  origin  adjusted  to  it. 
If  these  species  did  indeed  originate  where  we  now  find 
them,  and  in  the  present  geological  epoch,  the  argument 
might  at  least  be  entertained ;  but  this  is  not  the  fact. 
We  know  something  of  the  geological  history  of  all 
these  species,  and  the  history  of  the  migrations  of  some 
of  them.  We  know  that  sweet-gums  were  abundant 
and  of  many  species  in  the  United  States  in  Tertiary 
times,  and  all  have  become  extinct  excejit  this  remnant. 
Whatever  of  modifications  there  were  must  be  looked 
for  at  or  about  the  time  of  its  origin  in  Tertiary  times, 
not  now.  Species,  like  individuals,  are  j^l^stic  only 
when  young.  This  one  has  already  become  rigid,  and 
all  the  more  so  as  it  is  a  remnant  widely  separated  from 
other  species.  For  competition  is  strongest  and  most 
effective  with  nearest  allies.  Present  species  are  mostly 
isolated  remnants — terminal  twiglets  of  the  tree  of  life. 
Twiglets  are  of  course  widely  separated  at  their  visible 
ends.  Their  points  of  union  with  other  twiglets  must 
be  sought  below. 

In  the  case  of  the  sequoias,  we  know  something  also 
of  the  history  of  their  migrations.  In  Miocene  times 
they  were  abundant,  and  of  many  species  in  circumpolar 
regions.  Some  twent3^-four  species  of  fossil  sequoias 
are  known,  fourteen  of  which  are  Tertiar}-.  By  the 
cold  of  the  Glacial  epoch  they  were  driven  slowly  south- 


PROOFS  FROM  GEOGRAPHICAL  DISTRIBUTION".    203 

ward,  botli  in  America  and  in  Europe — in  America  as 
far  as  Southern  California.  After  the  Glacial  epoch,  and 
the  return  of  temperate  conditions,  they  doubtless  at- 
tempted to  go  northward  again  ;  but  these  great  changes 
were  too  much  for  them  ;  they  were  wholly  exterminated 
in  Europe,  and  nearly  so  in  America.  A  few  were  left 
stranded  high  up  on  the  slopes  of  the  Sierra  Nevada, 
and  on  the  cool,  moist  sloj^es  of  the  Coast  Eanges.  The 
species  now  in  California  are  not  identical  with  those 
found  in  the  Miocene  strata  of  Greenland  ;  but  the 
difference  is  only  what  we  might  expect  after  such  ex- 
tensive migrations  and  such  long  and  severe  struggle 
for  life.  Further,  it  is  noteworthy  that  the  Miocene 
species  fall  into  two  groups,  viz.,  the  yew-like  leaved 
and  the  cypress-like  leaved.  These  are  represented  to- 
day in  California,  the  one  by  the  redwood,  the  other 
by  the  big-tree.  They  are  evidently  direct  descendants 
of  the  Miocene  species,  though  somewhat  modified. 

But  it  will  be  objected  that  there  ought  to  be  some 
cases  of  transitional  forms  showing  transmutation — in 
fact,  there  ought  to  be  some  cases  of  species  now  form- 
ing under  our  eyes.  There  are,  we  believe,  examj^les 
of  such  cases.  But  intermediate  forms  are  not  likely 
to  be  maintained  long,  especially  if  migrations  occur 
to  give  rise  to  severe  conflict  of  forms.  In  that  case 
the  intermediate  forms  are  soon  eliminated,  and  species 
become  distinct.  This  important  point  will  be  dis- 
cussed more  fully  in  the  next  chapter. 


CHAPTER  VIIT. 

PROOFS     FEOM    ARTIFICIAL     PR0DUCTI0:N"    OF    VxVRIETIES, 

RACES,    SPECIES,    ETC. 

As  already  stated,  page  40,  the  use  of  the  method 
of  experiment  in  the  field  of  biology  is,  unfortunately, 
Yery  limited.  Neyertheless,  it  is  already  beginning  to 
be  used  more  and  more  in  the  department  of  physi- 
ology, and  may  be  used  also,  to  a  limited  extent,  in 
the  department  of  morphology.  It  is  true  that  direct 
scientific  experiments,  for  the  express  purpose  of  pro- 
ducing permanent  modifications  of  form,  and  thus  test- 
ing the  theory  of  evolution,  are  of  comparatively  little 
value  as  yet,  because  the  all-important  element  of  time 
is  wanting.  The  steps  of  evolution  are  so  slow,  and 
the  time  necessary  to  produce  any  sensible  effect  is  usu- 
ally so  great,  that,  in  comparison,  man's  individual 
lifetime  is  almost  a  vanishing  quantity.  But,  from 
time  immemorial,  experiments  have  been  unconsciously 
made  by  man  on  domestic  animals  and  food-plants, 
which  bear  directly  on  this  subject.  All  domestic  ani- 
mals and  food-plants,  and  many  ornamental  flowering 
plants,  have   been   subjected   for   ages   to   a   process   of 


PPvOOFo   FROM   ARTIFICIAL  PRODUCTION.      205 

artificial  selection  acting  upon  natural  yariation  of  off- 
spring. As  wild  species  are  modified,  we  believe,  in- 
definitely by  divergent  variation  and  natural  selection, 
so  domestic  species  are  modifiable  certainly  largely, 
perhaps  indefinitely,  by  divergent  variation  and  artifi- 
cial selection  by  man.  We  all  know  the  extraordinary 
modifications  which  have  thus  been  gradually  brought 
about  in  domestic  animals,  such  as  dogs,  horses,  sheep, 
pigeons,  etc.;  in  food-plants,  as  cereal  grains,  garden- 
vegetables,  etc.,  and  in  ornamental  jolants,  as  roses, 
dahlias,  pinks,  etc.  We  can  only  give  very  briefly  the 
principles  of  the  process  by  which  these  extreme  modi- 
fications are  i3roduced,  referring  the  reader  to  works 
specially  devoted  to  this  subject  for  more  complete  ac- 
counts. 

Let  it  be  borne  in  mind,  then  («),  that  inheritance 
is  not  only  from  the  immediate  parents,  but  from  the 
whole  line  of  ancestry.  The  inheritance  from  the  im- 
mediate parents  is,  doubtless,  usually  greater  than  from 
any  other  one  term  of  the  ancestral  series — the  effect 
on  the  offspring  of  any  previous  generation  becomes, 
doubtless,  less  and  less  as  the  distance  from  the  off- 
spring increases — yet  the  sum  of  the  ancestral  inherit- 
ance is  far  greater  than  the  immediate  jiarental.  Let 
it  also  be  borne  in  mind  {h)  that  true  breeding  from 
one  form  for  many  generations  creates  a  fund  of  he- 
redity in  that  form,  and  thus  tends  to  produce  fixity, 
rigidity,  or  permanence  in  that  form. 

Now,  the  method  of  producing  artificial  breeds,  some- 


206    EVIDENCES   OF  THE   TRUTH   OF  EYOLUTIOX. 

times  consciously,  sometimes  unconsciously,  is,  briefly, 
as  follows  :  Suppose  it  be  desired  to  obtain  a  yariety 
of  an  animal,  say  a  dog,  having  a  certain  character. 
We  start  from  a  common  type,  a  (Fig.  68).     If  this  type 


Tig.  CS. 


were  allowed  to  breed  naturally,  the  slight  divergent 
variation  of  offspring  represented  by  the  radiating  lines 
would  neutralize  one  another  by  interbreeding,  the  indi- 
vidual differences  would  be  ^^ poolecV  in  a  common 
stock,  and  the  S2:>ecies  would  remain  substantially  con- 
stant. But  if  among  all  these  slightly  divergent  vari- 
eties we  select  one,  1),  which  seems  in  the  right  direc- 
tion, and  ruthlessly  destroy  all  the  others  (indicated  by 
crossing  them  out  by  the  circular  line),  and  breed  this 
variety,  l,  only,  we  shall  get  again  a  number  of  di- 
vergent varieties.  It  may  be  that  the  larger  number 
of  these  will  be  backward,  in  the  direction  of  the  orig- 
inal type  «,  on  account  of  the  ancestral  heredity  in 
that  direction,  but  some  will  again  be  in  the  desired 
direction.  Let  all  the  varieties  other  than  the  desired 
one,  but  especially  the  backward-going  or  reverting 
ones,  be  again  destroyed,  and  the  one  kind  only  selected 
which  seems  to  be  in  the   right  direction,  viz.,  c.     As 


PROOFS  FROM  ARTIFICIAL  PRODUCTION.     207 

we  push  the  form  thus  from  generation  to  generation 
in  the  desired  direction,  especially  if  we  attempt  to 
hasten  too  much  the  process,  the  resistance  to  moye- 
ment — if  I  may  use  the  expression — in  that  direction 
becomes  greater  and  greater  (shown  by  the  decreasing 
distances  between  the  successive  points  of  divergence, 
a,  h,  c,  d,  etc.),  and  the  tendency  to  reversion  becomes 
stronger  (shown  by  the  greater  number  and  length  of 
the  backward-going  lines),  until  finally  it  is  almost 
impossible  to  push  any  farther.  We  will  su2')pose  that 
X  is  such  a  limit.  But  if,  now,  we  breed  true  on  the 
point  X,  destroying  tlie  reversions  or  backward  varia- 
tions for  many  generations,  we  will  gradually  accumu- 
late a  fund  of  ancestral  heredity  on  this  point  which 
increases  with  every  added  generation,  until  finally  the 
tendency  to  reversion  becomes  small.  The  variety 
'breeds  true  without  further  interference,  or  with  only 
very  general  superintendence.  Such  a  permanent  va- 
riety is  called  a  race.  After  a  race  is  firmly  established 
for  a  sufficient  length  of  time,  and  the  tendency  to 
reversion  is  lost,  it  may  itself  become  a  new  point  of 
departure  for  the  formation  of  new  varieties  or  races, 
in  the  same  or  other  directions.  Thus,  during  even  the 
brief  history  of  man,  have  been  formed  races  of  the 
different  domestic  animals,  and  useful  and  ornamental 
plants,  differing  so  greatly  from  each  other  that,  if  found 
in  the  wild  state,  they  would  unhesitatingly  be  called 
different  species,  or  even  in  some  cases  different  genera. 
Now,   if   art   can  vary  form   so   greatly,   and   in   so 


208    EVIDENCES   OF  THE  TEUTH   OF  EVOLUTION. 

short  time,  why  may  not  Nature  in  limitless  time  ?  If 
art  by  artificial  selection,  why  not  Nature  by  natural 
selection  ?  Nature  is  as  rigid  in  selection  and  as  ruth- 
less in  destruction  :  why  may  we  not  expect  similar  or 
even  much  greater  results  ?  The  process  is  similar  in 
the  two  cases — i.  e.,  selection  among  varieties  in  oil- 
spring,  only  that  the  selection  is  natural  instead  of 
artificial,  and  the  process  is  so  slow  that  there  is  little 
tendency  to  reversion  in  the  latter  case.  Suppose, 
then,  we  have  a  gradually  changing  physical  environ- 
ment, or  climate.  Among  the  divergent  varieties  of 
any  species  in  each  generation,  those  would  be  pre- 
served which  are  most  in  accordance  with  the  new 
climate,  and  the  others  would  perish.  This  is  natural 
selection,  or  survival  of  the  fittest.  Add  to  this  the 
effect  of  the  change  in  the  organic  environment.  All 
species  are  modified  by  the  changing  physical  environ- 
ment* but  these  modified  species  again  all  affect  one 
another  in  the  com2:)etitive  struggle  for  life,  and  the 
strongest  or  swiftest,  or  most  cunning,  survive  (natu- 
ral selection).  Add  to  this,  again,  the  struggle  among 
the  males  for  possession  of  the  females — for  reproductive 
opportunities — by  which  only  the  strongest  and  most 
courageous,  or  the  most  beautiful  and  attractive,  leave 
progeny  which  inherit  their  peculiarities  (sexual  selec- 
tion). Add  to  these,  finally,  ynigrations,  voluntary 
among  higher  and  involuntary  dispersals  among  lower 
animals  and  plants,  and  the  consequent  mingling  of 
faunas  and   floras — the  migrations   subjecting  them  to 


PROOFS   FROM   ARTIFICIAL   PRODUCTION.     209 

great  change  of  enyironment,  both  physical  and  or- 
ganic, and  the  mingling  ^^roducing  fiercer  struggle  for 
life — and  we  have  in  powerful  operation  many  causes 
of  modification.  Add,  I  say,  all  these  causes  of  modi- 
fication together,  and  then  make  the  process  slow  and 
continuous  through  unlimited  time,  and  where  is  the 
limit  to  the  degree  of  change  ?  Commencing  in  any 
species,  from  any  point  of  departure,  there  are  formed 
first  slight  modifications  which  would  be  called  yari- 
eties  ;  then  these  modifications,  continuing  in  the  same 
direction,  form  races ;  these  races  by  wider  separation 
become  species,  and  species  in  their  turn  become  gen- 
era, etc.  Comparing,  again,  to  a  growing  tree,  yari- 
eties  are  swelling  buds ;  when  they  grow  into  twigs, 
they  are  species  ;  when  they  branch  again  into  different 
species,  the  branching  stem  becomes  a  genus,  etc. 

We  haye  thus  far  spoken  only  of  the  yarious  forms 
of  one  factor,  yiz.,  the  Darwinian  factor  of  selection, 
whether  natural  or  artificial.  We  haye  dwelt  upon  this 
oncj  because  the  natural  and  the  artificial  processes  are 
so  similar,  and  the  artificial  is  so  controllable.  But  there 
are  other  factors  in  operation,  in  art  as  well  as  in  na- 
ture. We  haye  already  spoken  (p.  73)  of  other  factors 
of  natural  change.  We  haye  shown  how  changing 
physical  enyironment  affects  function,  and  function 
affects  form  and  structure^  and  how  these  slight 
changes  are  integrated  by  heredity  through  many  gen- 
erations. We  haye  also  showai  how  use  or  disuse  in- 
creases or  diminishes  the  size  and   change  the  form  of 


210    E\^IDENOES   OF  THE   TRUTH   OF  EVOLUTION 

parts,  and  these  changes,  also,,  however  slight,  are  in- 
tegrated by  heredity. 

Now,  these  factors  are  operative  also  in  domestication 
of  animals  and  cultivation  of  plants.  No  environment 
is  so  new  and  peculiar  as  domestication  and  cultivation. 
The  soil  and  temperature  in  plants,  food  and  housing  of 
domesticated  animals,  tend  to  change  form  and  structure 
of  the  offspring,  although  in  a  way  which  it  is  difficult 
intelligently  to  control,  and  thus  are  prolific  of  varieties 
from  which  to  select.  In  fact,  they  often  give  rise  to 
great  and  unexpected  modifications,  called  sports,  which 
form  jDoints  of  dejDarture  for  new  varieties  and  races. 
Now,  in  nature,  not  only  are  all  these  causes  and  factors 
of  change  in  constant  operation,  hut  they  act  together  in 
a  peculiarly  com2:)lex  way.  All  the  members  of  a  fauna 
and  flora,  and  the  physical  environment  of  any  locality, 
constitute  together  a  most  complex  and  delicately  ad- 
justed system  of  correlated  parts.  A  change  in  one  part 
is  propagated  through  the  whole  system  ;  also,  a  change 
in  one  factor  affects  all  other  factors.  When  we  add  to 
this  the  large  amount  of  time,  in  comparison  with  indi- 
vidual human  life  and  observation,  necessary  to  produce 
visible  change  of  form,  we  can  easily  understand  why  the 
process  is  still  imperfectly  understood,  although  tlie  fact 
is  certain. 

But  it  will  be  asked,  Are  there,  then,  no  differences 
between  the  artificially  made  extreme  varieties  equiva- 
lent, so  far  as  difference  of  form  is  concerned,  to  species, 
and  real  natural  species  ?    There  are.     If  there  were  not, 


PROOFS  FROM  ARTIFICIAL  PRODUCTION.     211 

tliere  would  neyer  have  been  any  doubt  about  the  deriva- 
tive origin  of  natural  species.  But  if  it  be  asked,  Are 
not  these  differences  fundamental,  and  therefore  fatal  to 
the  argument  for  evolution  derived  from  this  source  ? 
we  answer,  we  think  not.  We  will  deal  frankly  and 
fairly  with  these  differences. 

First  Difference,  Reversion.  —  The  strong  tendency 
of  artificial  varieties  to  reversion,  even  during  the  process 
of  formation,  and  especially  their  complete  reversion  to 
the  original  type  if  the  hand  of  man  be  withdrawn — i.  e., 
if  left  to  themselves,  or  become  wild — is  supposed  to  show 
an  essential  difference  between  such  varieties,  however 
extreme,  and  true  species — is  supposed,  in  fact,  to  prove 
an  indestructible  permanency  of  specific  types.  Nature 
disowns  these  artificial  forms,  and  as  it  were  brands  them 
with  bastardy.  Not  only  so,  she  strives  ever  to  destroy 
them.  The  supporting  hand  of  man  is  necessary  to 
sustain  them.  Left  to  themselves  and  to  Nature,  they 
quickly  revert  to  the  original  type.  If  all  the  extreme 
varieties  of  dogs,  from  the  greyhound  and  New^foundland, 
on  the  one  hand,  to  the  terrier  and  lap-dog  on  the  other, 
were  turned  loose  on  an  isolated  island,  uninhabited  by 
man  but  full  of  other  animals,  and  left  there  to  shift  for 
themselves — and  the  island  were  visited  again  after  a 
lapse  of  a  hundred  or  a  thousand  years — it  is  probable 
that  a  uniform  species,  something  like  to,  though  per- 
haps not  identical  with,  the  wolf,  would  be  found.  They 
would  have  reverted  to  the  original  or  nearly  the  origi- 
nal wild  type  from  which  they  were  produced  by  domes- 


212    EVIDENCES   OF   THE   TRUTH   OF  EVOLUTION. 

tication.     All  or  nearl}^  all  that  was  done  by  man  would 
have  been  undone  by  Nature.     This  reversion  is  one  test 

of  species. 

But  the  reason  of  this  tendency  to  reversion  is  ob- 
vious :  First,  the  time  was  too  short,  the  rate  of  change 
was  too  rapid,  in  the  artificial  formation  of  these  varieties. 
There  was  not  time  enough  to  accumulate  a  fund  of  he- 
redity on  each  successive  stage  of  the  change.  Therefore 
the  form  is  unstable  and  the  tendency  to  revert  is  strong. 
Compare  the  fleeting  days  and  the  hurrying  impatience 
of  man  with  the  infinite  time  and  the  divine  patience  of 
Nature  !  But  mere  instability  is  not  the  principal  cause 
of  reversion.  Secondly,  in  the  case  of  artificial  forms  in 
a  wild  state,  natural  selection  compels  7rversion.  Every 
species  in  a  wild  state  must  of  course  be  in  harmony  with 
the  environment.  But  artificially  made  forms  are  in 
harmony  with  the  artificial  environment  of  domestica- 
tion, but  not  with  the  environment  of  nature.  In  nature 
the  fittest  survive,  but  artificial  breeds  are  not  fit  to  sur- 
vive in  a  state  of  nature.  They  are  therefore  quickly 
destroyed  in  the  struggle  for  life,  or  must  be  modified. 
Nature  immediately  begins  to  select  the  fittest,  and 
gradually  in  the  course  of  time  ]3roduces  one  or  more 
uniform  species,  similar  to  that  from  which  they  came, 
or  perhaps  to  what  they  would  have  been  by  this  time  if 
left  to  the  operation  of  natural  causes  under  the  condi- 
tions supposed.  But  natural  species,  if  they  are  formed, 
as  the  derivationists  suppose,  by  the  operation  of  natural 
causes,  can  not  revert  unless  the  conditions  revert ;  for 


PROOFS   FROM  ARTIFICIAL  PRODUCTION.      213 

the  same  causes  which  operated  to  produce,  still  con- 
tinue to  operate  to  keep,  the  species.  Take  an  example  : 
The  form,  the  habits,  and  the  instincts  of  the  pointer 
have  been  made  by  a  slow  process  of  artificial  selec- 
tion of  diyergent  varieties  of  o:ffspring,  and  by  training  of 
individuals  continued  and  its  effects  accumulated  throusfh 
many  generations.  But  this  form  and  these  habits  and 
instincts,  so  laboriously  produced,  would  be  quickly  de- 
stroyed by  Nature.  The  pointer,  left  to  himself,  must 
either  change  or  become  extinct,  because  not  adapted 
to  the  wild  state.  Such  instincts  and  habits  would 
not  only  be  of  no  use,  but  would  be  incompatible  w^ith 
success  in  the  struggle  for  life.  But  suppose  for  a  mo- 
ment that  these  habits  and  instincts  were  useful  to 
the  animal  in  a  wild  state  ;  evidently  they  would  be  in- 
stantly seized  upon  by  natural  selection,  and  not  only 
perpetuated  but  intensified  until  a  very  distinct  species 
would  be  produced.  The  same  is  true  of  all  other  races 
of  dogs.  If  the  Newfoundland,  the  greyhound,  and  the 
pug  were  all  turned  loose  in  a  forest,  and  if  each  of  these 
kinds  were  admirably  adapted  to  some  place  in  the  econ- 
omy of  Nature — for  some  special  mode  of  food-getting 
without  corresponding  disabilities  in  other  directions  (as 
must  be  the  case  if  made  by  natural  selection) — there  can 
be  no  doubt  they  would  each  survive,  and  their  charac- 
ters intensified  ;  intermediate  forms  would  disapjDear  (for 
reasons  which  we  shall  see  presently),  and  we  would  soon 
have  three  distinct  species,  or  perhaps  we  would  even 
call  them  distinct  genera. 


214    EYIDEXCES   OF   THE  TRUTH   OF  EVOLUTION. 

Second  Diiferenee,  Intermediate  Forms,— Xatural  spe- 
cies are  distinct — marked  out  with  hard  and  fast  lines — 
while  artificiallj-made  races,  even  though  in  their  t}^ical 
forms  thej  differ  as  much  or  more  than  natural  sj^ecies, 
shade  into  one  another  bj  insensible  gradations.  In  an- 
swer and  exjolanation  of  this  difference  we  remark  :  If 
species  or  modified  forms  of  any  kind,  whether  natural 
or  artificial,  are  made  bv  natural  causes,  and  not  at  once 
out  of  hand  by  supernatural  creation,  then  of  course 
there  must  have  been  gradations  in  the  process  of  mak- 
ing. Now,  in  the  artificial  case,  the  whole  j)rocess  as 
well  as  the  result  lies  within  the  limits  of  observation, 
while  in  the  natural  case  onlv  the  final  result.  But  it 
will  be  asked,  Why  are  the  gradations  not  seen  also  in 
the  final  result  ?  We  answer,  because  the  intermediate 
forms  are  eliminated  in  the  struggle  for  life,  and  not  re- 
produced by  cross-breeding.  If  artificial  races  always 
bred  true — i.  e.,  without  crossing,  as  natural  species  do — 
they  would  j^robably  soon.be  as  sharj^ly  demarked.  Cross- 
breeding is  the  great  cause  of  the  shadings  between  do- 
mestic races.  This  brings  me  to  the  third  and  most  im- 
portant difference. 

Third  Difference,  Cross-Fertility.  —  Artificially-made 
races  breed  freely  and  without  repugnance  with  one  an- 
other, and  the  offspring  of  such  cross-breeding  is  in- 
definitely fertile.  Natural  species  will  not  usually  unite 
with  one  another,  being  prevented  by  sexual  repugnance 
and  other  causes.  Or,  if  they  do  sexually  unite,  there 
is  either  no  offspring,   or  else  the   offspring  is  sterile, 


PROOFS  FROM   ARTIFICIAL  PRODUCTION.      215 

and  therefore  the  intermediate  form  dies  out  in  the 
first  generation  ;  or  else  the  offspring  is  imperfectly 
fertile,  and  therefore  the  intermediate  form  is  elimi- 
nated in  a  few  generations,  and  the  species  remain 
distinct ;  or  else  the  offspring  is  more  fertile  with  the 
parent  stocks,  and  therefore  revert  to  the  parent  stocks^ 
and  still  the  species  remain  distinct.  Such  infertile,  or 
imperfectly  fertile,  offspring — the  result  of  crossing  of 
species — are  called  hybrids. 

This  is  regarded  as  a  most  important  test  of  true 
species,  as  contrasted  with  varieties  or  races.  There 
are  two  bases  on  which  species  may  be  founded.  Spe- 
cies may  be  based  on  form,  morphological  species  ;  or 
they  may  be  based  on  reproductive  functions,  physio- 
logical species.  By  the  one  method  a  certain  amount 
of  difference  of  form,  structure,  and  habit,  constitutes 
species ;  according  to  the  other,  if  the  two  kinds  breed 
freely  with  each  other  and  the  offspring  is  indefinitely 
fertile,  the  kinds  are  called  varieties,  but  if  they  do 
not  they  are  called  species.  The  two  tests,  however, 
do  not  always  accord.  Every  now  and  then  we  find 
undoubted  morphological  species  which  may  be  crossed 
and  produce  indefinitely  fertile  offspring.  Yet  it  is 
certainly  true  that  species  are  usually  cross-sterile,  while 
varieties,  whether  natural  or  artificial,  are  cross-fertile. 

In  explanation  of  this  important  difference,  let  it 
be  observed  that  there  are  here  two  things  which  must 
be  kept  distinct  in  the  mind,  although  they  are,  doubt- 
less, closely  allied — viz.,  sexual  repugnance  (psychologi- 


216    EVIDENCES   OF  THE   TRUTH  OF  EVOLUTION. 

cal  element)  and  cross-sterility  (physiological  element). 
The  former  is  fonnd,  of  course,  only  in  the  higher 
animals,  where  fertilization  is  voluntary.  The  latter  is 
universal  among  all  living  things.  This  latter,  there- 
fore, is  the  more  fundamental  and  essential  element, 
and  the  former  may  be  regarded  as'  its  psychical  sign 
in  the  higher  animals.  It  is  of  this  latter,  therefore — 
i.  e.,  cross-sterility — that  we  shall  speak  mainly. 

Suppose,  then,  w^e  have  growing  together  in  the  same 
locality  many  species  of  pines  or  oaks,  or  other  ane- 
mophilous  trees.  The  whole  air  is  filled  with  the  pollen 
of  many  species,  and  every  germ-cell  must  receive  many 
kinds  of  male  cells,  and  yet  there  are  no  hybrids,  but, 
on  the  contrary,  the  species  remain  distinct.  So  also 
in  case  of  hermaphrodite  animals,  where  the  fertilization 
is  involuntary ;  many  aquatic  species  are  found  together 
in  the  same  locality,  and  the  water  is  filled  with  sperm- 
cells  of  many  different  species.  Many  kinds  of  sperm- 
cells  must  fall  on  each  germ-cell,  and  yet  there  are  no 
hybrids ;  the  species  remain  distinct.  In  all  such  cases 
we  must  suppose  that  there  is,  among  the  different  kinds 
of  male  cells,  a  struggle  for  the  possession  of  the  germ 
or  female  cell,  or  a  sort  of  sexual  selection  by  the  female 
cell  among  the  competing  male  cells,  and  the  fittest — 
the  most  in  accord;  i.  e.,  those  of  the  same  species 
— prevail.  This  is  universal.  But  in  the  higher  ani- 
mals, in  addition  to  the  prepotency  of  male  cells  of  the 
same  species,  and  comparative  infertility  in  case  of  union 
of  those  of  different  species,  sexual  attraction  and  sexual 


PROOFS  FROM  ARTIFICIAL  PRODUCTION.     217 

repugnance  contribute  to  the  same  result,  and  species 
are  thus  doubly  separated.  Thus  sexual  selection  is  of 
two  kinds  :  selection  of  individuals  for  union  (psychical), 
and  selection  of  sperm-cells  for  fertilization  (physiologi- 
cal). The  one  kind  is  usually  the  sign  of  the  other — 
attraction  the  sign  of  fertility,  and  repugnance  of  sterility. 
But  in  the  domestic  state  it  is  all  otherwise.  Free 
competition  between  individuals  or  between  cells  is  not 
allowed.  Thus,  for  example,  among  plants,  crossings 
may  be  forced  and  hybrids  made  in  gardens  which  would 
never  occur  in  Nature.  The  florist  prevents  fertilization 
in  the  same  kind  and  compels  fertilization  of  a  different 
kind.  If  male  cells  of  the  same  kind  were  allowed  to 
compete,  the  result  would  be  different.  Doubtless  the 
same  method  would  succeed  in  many  lower  animals. 
So  also  in  higher  animals  free  competition  and  sexual 
selection  for  union  are  often  not  allowed,  and  therefore 
animals  of  different  species,  such  as  the  horse  and  the 
ass,  unite,  which  would  not  do  so  if  thev  were  free  to 
select  as  in  the  wild  state.  These  two  are  widely  dis- 
tinct si^ecies,  sometimes  even  called  genera,  and  there- 
fore the  offspring  is  infertile ;  but  two  closely  allied 
species,  such  as  two  species  of  wolf,  or  of  the  fox,  in  a 
domestic  state  would  probably  not  only  unite  but  pro- 
duce indefinitely  fertile  offspring.  In  fact,  it  is  almost 
certain  that  the  dog  was  made  by  a  mixture  of  several 
species  of  wolf,  most,  perhaps  all,  of  them  now  extinct.* 

*  "  Origin  of  Races  of  the  Dog."     *'  Annals  and  Magazine  of  Natural 
History,"  vol.  xvii,  p.  295.     1886. 


218    EVIDENCES   OF  THE   TRUTH   OF   EVOLUTION. 

On  the  other  hand,  it  is  not  at  all  certain  that  the 
extreme  varieties  of  dogs  have  not  passed  the  limit  of 
greatest  attraction,  and  therefore  of  greatest  cross-fer- 
tility, and  that,  if  allowed  free  choice,  as  in  Nature, 
they  would  not  breed  true,  or  tend  to  breed  true,  with 
their  own  kind,  and  intermediate  kinds  die  out  in  the 
struggle  for  life. 

Law  of  Cross-breeding". — Before  going  any  further  in 
this  discussion,  it  is  necessary  to  bring  out  another 
point  of  extreme  importance  in  the  formation  of  vari- 
eties, both  natural  and  artificial — a  point  which  I  be- 
lieve throws  light  upon  the  very  significance  of  sex 
itself — I  refer  to  the  effect  of  cross-breeding. 

It  is  a  curious  and  most  significant  fact  that  dif- 
ferent varieties,  both  natural  and  artificial,  are,  up  to 
a  certain  limit,  not  onlv  cross-fertile  and  cross-attract- 
ive,  but  even  more  so  than  mdividuals  of  the  same 
variety.  Long  experience  has  shown  that  very  close 
breeding  of  the  same  variety  for  a  long  time  fixes  the 
I'UiJ  but  iijeakens  the  stock,  especially  in  fertility,  while 
judicious  crossing  of  varieties  strengthens  the  stock, 
increasing  its  fertility,  and  especially  producing  plas- 
ticity or  variaMlity.  Therefore  breeders,  if  they  wish 
to  preserve  a  valuable  variety,  breed  close ;  but,  if  they 
wish  to  make  new  varieties,  cross-breed.  But  we  have 
already  seen  that  species  are  usually  cross-sterile.  There- 
fore there  must  be  some  regular  law  of  increase  to  a 
maximum,  and  again  decrease  to  zero.  It  is  this  law 
that  I  now  wish  to  investigate. 


PROOFS  EROM  ARTIFICIAL  PRODUCTION.      219 

In  the  lowest  animals  and  plants  multiplication  of 
individuals  and  the  continuance  of  the  kind  are  inde- 
pendent of  sex,  and  therefore  in  such  there  may  he  no 
sex  at  all.  The  sexual  elements  are  not  yet  differen- 
tiated. An  individual  divides  itself  into  tAvo ;  each 
grows  to  the  original  size  and  again  divides  into  two, 
and  so  on,  it  may  be  indefinitely.  In  this  lowest  form 
of  reproduction  the  individual  is  sacrificed  to  the  kind, 
or  else  we  may  regard  the  kind  as  an  extension  of  the 
individual,  and  reproduction  as  a  modification  of  growth. 
But  there  are  other  sexless  modes  of  reproduction,  found 
in  nearly  all  plants  and  many  lower  animals,  in  which 
the  individuality  is  not  sacrificed.  The  next  step  in 
the  ascending  scale  is  reproduction  by  hudding.  In 
this  case  a  bud  is  formed  which  grows  into  a  perfect 
individual,  and  may  remain  attached  to  the  parent 
stalk,  forming  together  a  compound  individual,  as  in 
most  plants  and  many  lower  animals,  such  as  the  coral; 
or  it  may  separate  and  assume  independent  life,  as  in 
some  plants  and  many  lower  animals.  In  still  other 
animals,  as  in  many  hydrozoa,  the  budding  function  is 
relegated  to  a  SjDCcial  part,  which  thus  becomes  a  re- 
productive organ.  The  next  step  is  the  placing  of  the 
budding  organ,  for  greater  safet}-,  in  an  interior  cavity. 
This  is  the  case  v/ith  aphids.  JSTow,  why  would  not 
this  be  an  excellent  mode  of  reproduction  for  all  ani- 
mals, man  included  ?  Why  was  sex  introduced  at  all  ? 
There  are  very  sufficient  reasons,  of  many  kinds,  which 
may  come   up   later ;   but   the   fundamental   reason,  in 


220    EVIDEN"CES   OF  THE   TRUTH   OF  EVOLUTION". 

connection  with  evolution,  is  the  funding  of  individual 
differe7ices  iii  a  common  offspring,  thereby  giving  to  the 
offspring  a  tendency  to  divergent  variation. 

Now,  non-sexual  re^DrocLuction  is  ahsolute  true  breed- 
ing. The  law  of  like  j)roducing  like  is  absolute.  He- 
redity is  all-powerful,  and  tendency  to  variation  is  nil. 
These  modes  of  reproduction  are  in  fact  but  a  modifica- 
tion of  growth  and  an  extension  of  the  individual.  Evo- 
lution-changes in  animals  produced  in  this  way  only 
must  be  very  slow,  since  the  most  powerful  factor  of 
evolution,  viz.,  natural  selection  among  divergent  varie- 
ties of  offspring,  would  be  wanting.  In  the  earliest  times, 
therefore,  before  sex  was  yet  declared,  we  may  imagine 
that  physical  environment  was  the  great  and  only  factor 
of  change.  Sexual  reproduction  introduces  the  new  ele- 
ment of  variation  of  offspring  from  which  Nature  makes 
her  selections  ;  and  this  element  of  variation  is  appar- 
ently the  result  of  the  union  of  diverse  individuals,  and 
the  funding  of  these  differences  in  a  common  offspring, 
and  thus  a  double  inheritance  of  individual  character- 
istics from  the  parents  and  a  multiple  inheritance  of  the 
same  from  the  ancestry.  See,  then,  with  this  end  in  view, 
the  pains  Nature  has  taken  to  make  the  difference  be- 
tween the  uniting  individuals  and  the  diversity  of  inher- 
itance by  the  offspring  as  great  as  possible,  and  yet  the 
gradual  way  in  which  she  has  accomplished  it.  As  al- 
ready said,  the  lowest  form  of  reproduction  is  that  by 
fission.  Next  comes  budding  in  any  part  indifferently. 
Next  comes  the  relegation  of  the  budding  function  to  a 


PROOFS  FROM  ARTIFICIAL  PRODUCTION.      221 

particular  part.  This  is  tlie  first  appearance  of  a  repro- 
ductive organ.  Next  comes  the  placing  of  this  organ, 
for  greater  safety,  within.  Thus  far  all  is  non-sexual 
reproduction — all  a  modification  of  growth — an  extension 
of  the  individual,  like  the  propagation  of  plants  by  cut- 
tings and  by  buds.  Then  comes  sexual  reproduction  in 
its  lowest  forms. 

It  may  be  well  to  stop  here,  to  show  the  entire  differ- 
ence between  this  and  non-sexual  modes.  The  latter,  we 
have  seen,  is  only  a  modification  of  growth,  an  extension 
of  the  individual.  Now,  sexual  reproduction  is  the  op- 
posite of  all  this.  Growth  is  a  constant  multiplication 
of  cells.  One  cell  is  ever  becoming  two  similar  cells — or, 
if  we  call  them  individuals,  one  individual  is  ever  becom- 
ing two  similar  individuals.  But  in  sexual  reproduction 
we  have  an  exactly  reverse  process.  Reduced  to  its  sim- 
plest terms,  sexual  reproduction  is  the  fusion  of  tivo  di- 
verse cells,  sperm-cell  and  the  germ-cell,  to  form  one  cell, 
the  ovule — literally,  a  diverse  twain  forming  one  flesh. 
In  its  higher  forms  it  is  the  union  of  diverse  individuals 
to  bring  about  the  same  result.  Instead  of  one  cell  be- 
coming two,  it  is  two  cells  becoming  one  ;  instead  of  one 
individual  becoming  two  in  the  offspring,  it  is  two  indi- 
viduals becoming  one  in  the  offspring.  But  this  great 
change  was  not  brought  about  at  once,  but  only  in  the 
most  gradual  manner.  First,  the  sexual  elements — sperm- 
cell  and  germ-cell — are  separated,  but  in  the  same  organ. 
Then  the  organs — spermary  and  ovary — are  separated, 
but  in  the  same,  individual.    This  is  the  condition  of  self- 


222  EVIDENCES   OF  THE   TRUTH   OF  EVOLUTION. 

fertilizing  hermaphroditism  so  common  among  plants 
and  lower  animals.  Then  comes  cross-fertilizing  her- 
maphroditism ;  and  Nature  takes  much  pains  and  uses 
many  ingenious  devices  to  prevent  self-fertilization  and 
insure  cross-fertilization.  Now,  for  the  first  time,  we 
have  slight  individual  differences  funded  in  a  common 
offspring.  Then,  in  order  to  absolutely  forbid  self-fertili- 
zation, and  at  the  same  time  allow  greater  differences  in 
the  crossing  individuals  than  could  be  attained  in  her- 
maphroditic individuals,  the  sex  organs  are  separated  in 
different  individuals,  and  fertilization  can  only  take 
place  by  voluntary  union.  Then,  to  insure  the  nnion  of 
suitable  individuals,  and  forbid  the  ban  between  unsuit- 
able, there  are  introduced  sexual  attraction  and  repulsion. 
Then,  last  of  all,  the  difference  between  the  two  sex- 
individuals  becomes  greater  and  greater  as  we  go  up.  It 
is  conspicuous  only  in  yertebrates  and  some  insects,  and 
very  conspicuous  only  in  birds  and  mammals. 

We  see,  then,  as  we  go  up  the  taxonomic,  and  undoubt- 
edly also  the  phylogenic  series,  that  there  is  a  cross- 
breeding of  more  and  more  diverse  individuals,  a  funding 
of  more  and  more  divergent  characteristics  in  a  common 
offspring.  Why  is  this  ?  I  answer,  for  the  sake  of  bet- 
ter results  in  the  offspring.  This  is  abundantly  shown 
by  direct  experiment.  In  hermaphroditic  plants  in  which 
there  may  be  either  self-fertilization  or  else  cross-fertiliza- 
tion with  other  individuals  of  the  same  species,  the  latter 
produces  better  results  in  number  and  vigor  of  offspring. 
But  there  are  other  advantages,  more  difficult  to  prove 


PPwOOFS   FROM   ARTIFICIAL   PRODUCTIOX.      223 

but  none  tlie  less  certain,  and  of  the  greatest  importance 
in  evolution  :  First,  as  already  stated,  complexity  of  in- 
heritance, like  complexity  of  composition  in  a  chemical 
substance,  gives  instability  to  the  embryo,  and  thus  lia- 
bility to  variation  in  the  offspring;  and  this  in  its  turn 
furnishes  the  material  for  selection  of  the  fittest.  Again, 
it  seems  to  me  that  there  is  a  direct  tendency  to  improve 
the  offspring  by  a  sort  of  struggle  in  the  embryo  among 
the  various  qualities  inherited  from  both  sides,  and  a 
survival  of  the  best  and  strongest — a  sort  of  pre-potency 
of  strong  qualities. 

Can  divergence  of  uniting  individuals  and  the  fund- 
ing of  diverse  characteristics  go  any  further  ?  It  may. 
The  differences  of  the  unitinsr  individual  mav  be  still  fur- 
ther  increased,  and  the  resulting  offspring  still  further 
improved  by  the  cross-breeding  of  different  varieties  of 
the  same  species,  for  we  thus  add  varietal  differences  to 
sexual  differences  in  the  uniting  individuals.  It  is  well 
known  that  too  close  breeding,  or  consanguineous  breed- 
ing, or  breeding  in  and  in,  as  it  is  variously  called,  if 
continued  long,  has  a  bad  effect  on  the  offspring,  weaken- 
ing the  stock,  while  judicious  crossing  of  varieties  w^ithin 
certain  limits  of  difference  has  a  good  effect,  strengthen- 
ing the  stock  and  increasing  its  fertility.  It  probably 
does  so  in  two  ways  :  one  direct,  by  funding  many  diverse 
qualities  from  both  sides,  and  the  survival  in  the  off- 
spring of  the  strongest  and  best ;  the  otlier  indirect,  by 
giving  plastirAfy,  instability  to  the  embryo,  and  varia- 
bility to  the  offspring,  and  therefore  abundant  material 
11 


22i    EVIDENCES   OF   THE   TRUTH   OF  EVOLUTION. 

for  tlie  operation  of  selection,  either  bj  man  or  by  Na- 
ture. We  said,  "  within  certain  limits  of  difference."  If 
the  difference  is  extreme,  as  in  extreme  varieties  and 
races,  then  the  effect  becomes  again  bad,  and  more  and 
more  so  as  the  limit  of  specific  difference  is  approached  ; 
at  which  limit  at  last  Nature  shuts  down  and  forbids  the 
bans.  Thus,  then,  there  is  in  cross-breeding  a  regular  law 
of  effect,  increasing  to  a  maximum  and  again  decreasing, 
which  may  be  gra23hically  represented  by  a  curve  (Fig. 
69).     In  this  figure  tlie  horizontal  line  represents  the  or- 


FiG.  69. 
dinary  level  of  the  type  ;  distances  on  this  line  represent 
differences,  individual,  varietal,  or  specific  ;  ordinates 
above  or  below  represent  the  effect,  good  or  bad,  of  cross- 
ing. Thus  s  s'  represent  two  species,%nd  the  line  between 
represents  their  specific  differences ;  r  r'  represent  differen  t 
races  or  permanent  varieties  ;  v  v'  two  strong  varieties  ; 
d  cV  ordinary  individual  differences  ;  c  c'  close  resembling 
or  consanguineous  individuals.  The  undulating  line  rep- 
resents the  effect  of  crossing  these  various  kinds.  It  is 
seen  that  *^  in-and-in  breeding,"  c  c',  produces  bad  effect 
(negative  ordinates)  ;  breeding  of  ordinary  individual 
differences,  dcT,  keeps  the  stock  at  the  ordinary  level — in 
its  typical  form  ;  crossing  two  strong  varieties,  v  v',  pro- 
duces maximum  good  effect  (positive  ordinates)  ;  crossing 


PROOFS  FROM  ARTIFICIAL  PRODUCTION.     225 

decided  races  produces  again  bad  effects,  which  become 
infinitely  bad  as  we  approach  species,  s  s'.* 

It  is  generally  admitted  that  long-continued  very  close 
breeding  has  a  bad  effect.  Even  in  plants,  Darwin  has 
shown  that  cross-fertilization  has  better  effect  than  self- 
fertilization,  this  last  being  of  course  the  closest  possible 
breeding.  But  it  is  probable  that  the  principal  bad  effect 
is  not  on  the  stock  but  on  the  process  of  evohttion.  Very 
close  breeding  weakens  the  stock,  ordinary  breeding  of 
individual  differences  maintains  the  stock  at  the  or- 
dinary level  and  fixes  it.  Cross-breeding  of  varieties 
strengthens  the  stock,  and  also  (and  this  is  its  main 
advantage)  produces  23lasticity  in  the  stock,  gives  rise  to 
strong  divergent  variations,  or  even  sports,  and  thus  be- 
comes a  main  agent  in  evolution.  It  is  j^robable,  more- 
over, that  the  higher  the  function  the  more  sensitive  is  it 
to  these  effects  of  breeding.  Therefore,  the  effect  is  great- 
er in  man  than  in  any  other  animal.  It  is  true  that  many 
have  doubted  the  bad  effect  of  close  breeding  in  man, 
and  have  brought  forward  formidable  statistics  to  substan- 
tiate their  position  ;  but  these  doubtless  take  no  account 
of  the  most  imj)ortant  function,  the  psychic,  and  espe- 
cially the  most  important  element  in  every  function,  so 
far  as  evolution  or  j)rogress  is  concerned,  viz.,  plasticity 
or  capability  of  progressive  improvement.  The  tendency 
of  consanguineous  breeding,  or  even  the  breeding  of  per- 


"  Mr.  Galton  ("  Nature,"  August  26,  1886)  has  used  a  diagram  simi- 
lar to  the  above  (which  I  first  used  in  1879)  to  illustrate  the  law  of 
sexual  attraction  and  repugnance. 


226   EVIDENCES   OF  THE   TRUTH   OF  EVOLUTION. 

sons  of  like  character  and  experiences,  as  in  an  isolated 
community,  is,  if  not  to  deteriorate  the  physique,  at  least 
to  fix,  stereotype  the  character,  and  thus  to  check  social 
progress.  Contrarily,  the  crossing  of  Yarieties  of  the 
same  race  seems  not  only  to  strengthen  but,  by  the  diverse 
inheritance,  to  produce  plasticity  of  character  and  ca- 
pacity for  progress.  But  the  difference  between  the  pri- 
mary races  seems  too  great  for  crossing  with  advantage. 
Some  degree  of  sexual  repugnance  which  undoubtedly 
exists  between  the  primary  races  is  the  psychical  sign  of 
this  fact.* 

If,  now,  we  go  back  to  what  we  said  before  taking  up 
this  subject  of  the  effect  of  cross-breeding,  we  at  once  see 
that  there  is  an  apparent  flaw  in  all  our  reasonings.  If 
close  in-and-in  breeding  produced  better  and  more  nu- 
merous offspring  than  cross-breeding  between  slight  va- 
rieties, then,  indeed,  such  varieties  would  be  preserved, 
and  increase  in  divergence  from  generation  to  genera- 
tion until  they  became  species.  Or,  in  any  case,  if,  in 
any  way,  divergence  could  reach  the  point  of  extreme 
varieties  or  races,  or  what  are  called  sub-species,  then 
commencing  cross-sterility  Avould  complete  the  separa- 
tion, and  thus  form  true  species.  But  how  can  the  pro- 
cess of  progressive  divergence  begin,  when  slight  varie- 
ties are  even  more  fertile  by  cross-breeding  than  by  close 
breeding  ?    Is  it  not  evident  that,  with  every  generation, 

*  This  subject  is  more  fully  discussed  )3y  the  author  in  an  article  en- 
titled "  Genesis  of  Sex,"  in  "  The  Popular  Science  Monthly,"  vol.  xvi,  p, 
167,  1879. 


PROOFS  FROM  ARTIFICIAL   PRODUCTIOX.     227 

the  slight  Yarieties  would  cross-breed  with  one  another 
and  with  the  parent  stock,  and  thus  all  varietal  differ- 
euces  would  be  funded  into  a  common  stock,  and  the 
type  would  be  preserved  unchanged  ?  This,  as  already 
pointed  out  (p.  76),  has  always  been  the  chief  difficulty 
in  the  way  of  imagining  how  varieties  can  grow  into  spe- 
cies ;  and  the  difficulty  is  only  increased  by  our  discus- 
sion of  the  law  of  cross-breeding.  Xow,  just  here,  Dr. 
Romanes's  most  important  and  prolific  idea  comes  to  our 
help,  and,  as  it  seems  to  us,  completely  solves  the  diffi- 
culty. 

According  to  Dr.  Romanes,  no  organ  is  so  subject 
to  variation  as  the  reproductive,  and  this  in  no  resjoect 
so  much  as  in  degrees  and  kinds  of  fertility — we  might 
almost  say  so  subject  to  freaks  of  cross-sterility.  Now, 
suppose  we  start  with  any  well-defined  species  in  a  state 
of  nature.  With  every  generation  there  are  many 
slightly  divergent  individual  varieties,  some  greater  and 
some  less  ;  but  these  are  all  immediately  swamped  by 
crossing  with  one  another  and  with  the  parent  stock, 
and  the  species  remains  unchanged.  But  suppose  among 
these  divergent  variations  there  arise,  from  time  to 
time,  some  which  affect  the  reproductive  organs  in  such 
wise  that  the  variety,  though  perfectly  fertile  with  its 
own  kind,  is  infertile,  or  imperfectly  fertile,  with  other 
varieties,  and  especially  with  the  parent  stock.  The 
change  may  be  only  in  the  time  of  flowering  in  plants, 
or  season  of  heat  in  animals,  or  it  may  be  actual  in- 
fertility in  sexual  union.      Right  here  we  have  the  be- 


228    EYIDEXCES   OF   THE   TRUTH   OF   EVOLUTION. 

ginning  of  a  new  species.  The  variety  is  sexnallv  iso- 
lated from  the  parent  stock  by  cross-sterility,  and 
therefore  all  its  peculiarities,  however  trivial,  are  pre- 
served by  true  breeding.  Cross-breeding  is  necessary  to 
make  species,  but  true  breeding  preserves  them.  Cross- 
breeding tends  ever  to  make  varieties,  but  immediately 
destroys  them  again.  This  constant  forming  and  swamp- 
ing, separating  and  again  merging  of  varieties,  like 
mixing  of  dough,  makes  the  whole  mass  (stock)  more 
and  more  plastic  and  subject  to  variety.  This  plas- 
ticity finally  gives  rise  to  varieties  of  the  kind  which 
produces  specie3  by  sexual  isolation.  By  continued 
merging  the  centrifugal  forces  continually  increase,  but 
are  continually  repressed  by  crossing,  until  finally  vari- 
eties break  away  to  form  species. 

'Now  it  IS  easy  to  see,  from  this  point  of  view,  why 
artificial  varieties  are  cross-fertile.  It  is  because  in 
artificial  breeding  we  are  intent  only  on  making  vari- 
eties in  form,  size,  color,  etc.,  and  not  at  all  on  making 
any  characterized  by  cross-sterility  with  the  parent 
stock.  Cross-sterility  with  the  parent  stock,  or  with 
other  varieties,  would  be  of  no  advantage,  because  we 
control  the  breeding,  and  can  breed  true  if  we  desire. 
Sexual  isolation  is  not  necessarv,  because  we  can  use 
physical  isolation.  On  the  contrary,  such  cross-sterility 
would  be  a  positive  disadvantage  to  the  breeder,  by 
limiting  the  range  of  his  experiments  just  where  they 
would  be  most  prolific  in  making  new  varieties.  Hence, 
as  might  be  expected,  all  domestic  varieties  are  cross- 


PROOFS   FROM   ARTIFICIAL  PRODUCTION.     229 

fertile,  unless  it  be  the  extreme  varieties,  which  may, 
ill  some  instances,  have  passed  the  limit  of  greatest 
fertility. 

If  this  idea  be  true,  then  species  which  have  origi- 
nated in  the  same  locality  ought  to  be  always  cross- 
sterile,  but  species  which  have  grown  up  apart,  in  widely 
separated  geographical  regions,  ought  to  be  sometimes 
cross-fertile,  because  they  were  isolated  by  physical  not 
by  sexual  barriers.  Such,  Dr.  Romxanes  thinks,  is  a  fact. 
It  is,  however,  a  very  important  point,  which  ought  to 
be  carefully  investigated.  We  say  ''sometimes.^''  It  is 
probable  that  mo:t  geographical  species  also  are  cross- 
sterile  ;  for,  although  the  isolation  by  cross-sterility  of 
slight  varieties  be  the  main  cause  of  the  origin  of  species, 
yet  a  species  formed  by  isolation  of  any  other  kind 
will  gradually  become  cross-sterile  with  other  species. 
Although  cross-sterility  be  the  main  cause  of  divergence, 
yet  divergence  beyond  a  certain  limit,  however  caused, 
will  bring  about  cross-sterility,  because  the  reproductive 
organs  will  i3artake  of  the  general  change  going  on  in 
every  part. 

Application. — Suppose,  then,  a  species  breeding  natu- 
rally in  a  wild  state.  Individual  varieties  are  constantly 
being  formed  and  again  funded  back  into  the  common 
stock  by  cross-breeding.  If  the  varieties  thus  formed 
be  decided,  the  cross-breeding  will  strengthen  the  stock, 
and  especially  will  preserve  and  increase  its  plasticity  or 
tendency  to  variation.  Finally,  among  the  widely  di- 
vergent varieties  there  is  one  affecting  the  reproductive 


230    EVIDENCES   OF   THE   TRUTH   OF   EVOLUTION. 

organs  of  several  individuals  in  such  wise  that  they  are 
infertile,  or  imperfectly  fertile,  with  the  parent  stock, 
though  perfectly  fertile  among  themselves.  These  form 
a  new  species,  which  continue  to  increase  indefinitely. 

Ohjection  answered. — This  view  completes  the  answer 
to  an  objection  which  is  often  made  to  evolution  :  *'  If 
natural  sj)ecies  are  formed  by  transmutation,  why  is  it 
we  do  not  find  intermediate  links  ?  Why  is  not  organic 
nature  made  wp  only  of  individual  forms,  shading  in- 
sensibly into  each  other  in  such  wise  that  classification 
becomes  a  mere  device  to  handle  more  conveniently 
complex  material  ?  Why  is  it  that  groups,  especially 
species,  are  marked  out  with  hard  and  fast  lines  ?" 
We  have  heretofore  answered  this  by  saying  that  inter- 
mediate forms  are  eliminated.  So  they  are,  but  how  ? 
Dr.  Romanes's  idea  of  physiological  selection  largely 
answers  this.  It  is  by  the  funding  of  ordinary  varie- 
ties into  a  common  parental  stock  by  crossing,  and 
separating  specific  varieties  by  cross-sterility.  Thus  the 
organic  field  is  broken  up  into  points  about  which 
variations  oscillate.  As  every  mass  of  matter,  when 
closely  examined,  is  found  to  consist  of  aggregations 
about  centers  of  cohesive  attraction  as  discrete  granules 
or  crystals,  and  only  exceptionally  do  we  find  a  homo- 
geneous vitreous  structure ;  even  so  organic  forms  ag- 
gregate about  points  of  sexucil  attraction,  and  the  whole 
mass  consists  of  discrete  species,  and  only  exceptionally 
— i.  e.,  in  domestication — do  we  find  insensible  shad- 
ings.    Now,  species  are  the  smallest  aggregate  of  indi- 


PROOFS  FROM  ARTIFICIAL  PRODUCTION.      231 

viduals,  as  granules  are  of  molecules.  Species  are  more 
distinctly  marked  out  by  hard  and  fast  lines  than  are 
other  taxonomic  groups  only  because  they  are  the  last, 
going  downward,  that  are  cross-sterile — because  right 
here  is  the  change  from  cross-sterility  to  cross-fertility. 

If  this  yiew  be  true,  then  in  the  same  locality  spe- 
cies ought  to  be  always  distinct  and  without  shadings. 
If  we  find  shadings  at  all,  it  ought  to  be  in  interme- 
diate geographical  regions,  where  isolation  is  not  sexual 
but  physical.  Now,  this  is  exactly  what  we  find  to  be 
the  fact.  hmumeraUe  examples  of  such  intermediate 
forms  in  i^itermediate  geographical  regions  are  now 
known,  especially  among  birds  and  reptiles,  and  exam- 
ples have  so  increased  in  modern  times,  by  closer  study, 
that  naturalists,  especially  ornithologists,  have  been  com- 
pelled to  resort  to  a  trinomial  nomenclature  in  order 
to  designate  these  geographical  sub-species.* 

If  any  further  explanation  is  necessary,  it  will  prob- 
ably be  found  in  the  following  suggestions  : 

1.  The  number  of  individual  varieties  constantly 
being  formed  is  almost  infinite,  but  the  number  of 
places  in  nature  is  very  limited.  Now,  among  the  in- 
finite number  of  slight  individual  varieties  formed  with 
every  generation,  the  competitive  struggle  will  be  se- 
verest between  those  most  nearly  alike,  because  they  are 
competitors  for  the   same   place.      Only  one  kind  suc- 


*  For  examples  of  this  the  reader  is  referred  to  Cope,  "  Bulletin  of 
the  National  Museum,"  No.  1 ;  and  to  Coues's  "  Key  to  North  American 
Birds,"  last  edition. 


232    EVIDENCES   OF   TPIE   TRUTH  OF   EVOLUTION. 

ceeds,  viz.,  the  fittest.  Intermediate  forms  are,  there- 
fore, exactly  those  which  are  eliminated  in  the  most 
wholesale  way.  2,  Add  to  this  the  fact  that,  as  soon 
as  divergence,  from  whatsoever  cause,  reaches  a  certain 
point,  sexual  repugnance  or  cross-sterility,  or  both,  come 
in  to  i^erpetuate  and  increase  the  separation  already 
commenced.  3.  Add  to  this,  again,  that  migrations  in 
higher  animals,  and  involuntary  dispersals  in  lower  ani- 
mals and  in  plants,  and  the  mingling  together  of  dif- 
ferent faunas  and  floras,  produces  a  still  fiercer  struggle 
for  life,  especially  between  natives  and  invaders,  and 
thus  great  numbers  of  forms  are  destroyed  ;  all  but  the 
fittest  are  weeded  out,  and  therefore  the  distinctness  of 
the  remainder  is  greatly  increased.  Periods  of  great 
changes  of  physical  geography  and  of  climate,  and  there- 
fore of  wide  and  general  migrations,  are  also  periods 
of  great  weedings-out  of  unfit  forms.  Thus  it  happens 
that  existing  faunas  and  floras  are  little  else  than  iso- 
lated remnants. 

To  illustrate,  again,  by  a  growing  tree  :  If  all  the 
buds  of  a  tree  lived  and  grew,  they  would  soon  become 
so  numerous  that  they  would  together  form  a  solid 
hemispherical  mass,  like  a  coral-head,  with  no  room 
between  for  leaf  or  light  or  air.  But  ninety-nine  one- 
hundredths  of  buds  die  in  the  strusfslo  for  lio^ht  and 
air,  and  therefore  the  survivors  are  distinct  growing 
points,  widely  separated  from  each  other.  Species  are 
such  extreme,  but  separated,  twiglets  of  the  tree  of  life. 

Objection. — But  it  will  be  objected,  again  :  The  twig- 


PEOOFS  FROM  ARTIFICIAL  PRODUCTION.     233 

points  are,  indeed,  separate,  but  the  twigs  themselves 
must  meet  somewhere  lower  down,  where  they  began 
to  grow.  Intermediate  links  may  be  w^anting  noiv,  but 
they  must,  of  course,  have  existed  once — i.  e.,  in  pre- 
vious geological  times,  and  therefore  ought  to  be  found 
fossil.  In  distribution  in  space  or  geographically,  organic 
kinds  may  be  marked  oS  by  hard-and-fast  lines,  but, 
if  their  derivative  origin  be  true,  in  their  distribution 
in  time  or  geologically,  there  ought  to  be  many  examples 
of  insensible  shadings  between  them.  In  fact,  if  we 
only  had  all  the  extinct  forms,  the  organic  kingdom, 
taken  as  a  whole  and  throughout  all  time,  ought  to 
consist  not  of  species  at  all,  but  simply  of  individual 
forms,  shading  insensibly  into  each  other,  like  the  colors 
of  the  spectrum,  and  our  classification  ought  to  be  a  mere 
matter  of  convenience,  having  no  counterpart  in  nature. 
But  this  is  not  the  fact.  On  the  contrary,  the  law  of 
distribution  in  time  is  apparently  similar  in  this  respect 
to  the  law  of  distribution  in  space,  already  given  (page 
169).  As  in  the  case  of  contiguous  geographical  faunas, 
the  change  is  apparently  by  substitution  of  one  species 
for  another,  and  not  by  transmutation  of  one  species 
into  another.  So  also  in  successive  geological  faunas, 
the  change  seems  rather  by  substitution  than  by  trans- 
mutation. In  both  cases  species  seem  to  come  in  sud- 
denly, with  all  their  specific  characters  perfect,  remain 
substantially  unchanged  as  long  as  they  last,  and  then 
die  out  and  are  replaced  by  others.  Certainly  this 
looks   much   like   immutability   of    specific   forms,    and 


23i    EVJDENCES   OF  THE   TRUTH   OF  EVOLUTION. 

supernaturaHsm  of  specific  origin.  We  have,  we  be- 
lieve, satisfactorily  explained  this  in  the  case  of  geo- 
graphical distribution  (page  201),  but  how  can  we  ex- 
13lain  it  in  the  case  of  geological  distribution  ? 

Answer. — 1.  The  reason  for  this,  given  by  Darwin 
and  other  evolutionists,  is  the  extremely  fragmentary 
character  of  the  geological  record.  If  the  existing 
faunas  and  floras  are  but  isolated  remnants,  the  rest 
having  been  destroyed  by  migrations  and  conflicts,  how 
much  more  are  fossil  faunas  and  floras  but  fragmentary 
remnants,  the  rest  having  been  lost,  partly  because  never 
preserved,  and  partly  by  destruction  of  the  record  !  If 
from  this  cause  existing  species  are  widely  separated, 
how  much  more  ought  we  to  expect  to  find  fossil  species 
distinct  and  widely  separated  ! 

This  is  undoubtedly  in  most  cases  a  true  and  suffi- 
cient answer,  yet  we  think  the  fragmentariness  of  the 
geological  record  has  been  overstated.  While  it  is  true 
that  there  are  many  and  wide  gaps  in  the  record ;  w^iile 
it  is  true,  also,  that  even  where  the  record  is  continiious 
many  forms  may  not  have  been  preserved,  yet  there  are 
some  cases,  especially  in  the  Tertiary  fresh-water  de- 
posits, where  the  record  is  not  only  continuous  for  hun- 
dreds of  feet  in  thickness,  but  the  abundance  of  life 
was  very  great,  and  the  conditions  necessary  for  preser- 
vation exceptionally  good.  In  such  cases  the  number 
of  fossil  species  found  on  each  horizon  seems  to  be  as 
great  as  in  existing  faunas  over  equal  space.  The  rec- 
ord in  these  cases  seems  to  be  continuous  and  without 


PROOFS   FROM  ARTIFICIAL  PRODUCTION".      235 

break,  and  crowded  with  fossil  forms  ;  and  yet,  although 
the  species  change  greatly,  and  perhaps  many  times,  in 
passing  from  the  lowest  to  the  highest  strata,  we  do 
not  usually,  it  must  be  acknowledged,  find  the  gradual 
transitions  we  would  naturally  expect,  if  the  change 
v/ere  effected  by  gradual  transformations.  The  incom- 
pleteness  of  the  record,  therefore,  although  a  true  and 
important  cause,  is  not  the  whole  cause. 

In  further  and  completer  answer  to  this  greatest  of 
all  objections,  we  will  throw  out  the  following  sug- 
gestions : 

2.  We  must  remember  that  considerable  latitude  is 
allowed  by  the  anti-derivationists  to  variation  of  species  ; 
so  much  so,  indeed,  that  it  is  often  difficult  to  draw  the 
line  between  well-marked  varieties  and  closely-allied  spe- 
cies. Now,  according  to  the  derivationist,  these  strong 
varieties,  breeding  usually  true,  are  naught  else  than 
commencing  species. 

3.  On  every  side  and  everywhere,  both  m  existing 
faunas  and  in  fossil  forms,  but  especially  in  the  latter, 
we  find  innumerable  examples  of  transitions,  or  inter- 
mediate forms,  between  all  the  Mglier  groups,  such  as 
genera,  families,  orders,  and  classes.  It  is,  m  fact,  by 
means  of  these  that  the  great  law  of  differentiation 
from  generalized  types  has  been  established.  It  is, 
therefore,  only  between  species  that  such  intermediate 
forms  are  rare. 

4.  But  even  between  species  such  intermediate  forms, 
though  rare,  have  been  pointed  out,  both  in   existing 


236   EVIDENCES   OF  THE   TRUTH   OF  EVOLUTION". 

and  in  extinct  faunas.  But  the  opposition  contend  that, 
in  all  such  cases,  the  previously  supposed  species  are 
only  varieties.  We  have  already  (page  61)  spoken  of 
the  obvious  fallacy  involved  in  this  position.  Species 
are  fii^t  defined  as  forms  distinct  and  without  inter- 
mediate links,  and  then  we  are  challenged  to  find  such 
links ;  and  when,  with  much  labor,  we  find  them,  they 
say  the  supposed  species  are  not  species,  but  only  vari- 
eties. But  there  are  some  cases  in  wliich  this  subterfuge 
will  not  do.  There  are  cases  in  which  the  transitions 
are  between  forms  so  extreme  that  they  can  not,  by  any 
stretch  of  the  term,  be  called  varieties.  "W'e  will  select 
and  dwell  upon  but  one  striking  example,  viz.,  the  fossil 
forms  of  the  Tertiary  fresh-water  deposits  of  Steinheim. 
In  Wiirtemberg,  near  the  little  village  of  Steinheim, 
are  found  certain  strata  of  sand  and  lime,  which  are  evi- 
dently deposits  from  a  small  lake  of  Tertiary  times.  The 
deposits  are  extremely  rich  in  fossil  shells,  especially  of 
the  different  species  of  the  genus  Planorbis.  As  the  de- 
posits seem  to  have  been  continuous  for  ages,  and  the 
fossil  shells  very  abundant,  this  seemed  to  be  an  excel- 
lent opportunity  to  test  the  theory  of  derivation.  With 
this  end  in  view,  tliey  have  been  made  the  subject  of  ex- 
haustive study  by  Hilgendorf  in  1866,*  and  by  Hyatt  in 
1880. f     In  passing  from  the  lowest  to  the  highest  strata 

*  "  Monatsbericlit  d.  k.  Preuss.  Akademie  d.  Wisscnschaft  zu  Berlin," 
for  July,  1866. 

\  "Genesis  of  Tertiary  Species  of  Planorbis  at  Steinheim."  A.  Hyatt, 
Anniversary  Memoir  of  the  Boston  Society  of  Natural  History,  1880. 


PROOFS  FROM  ARTIFICIAL  PRODUCTION.      237 

the  species  change  greatly  and  many  times,  the  extreme 
forms  being  so  different  that  were  it  not  for  the  inter- 
mediate forms  they  would  be  called  not  only  different 
species  but  different  genera.  And  yet  the  gradations  are 
so  insensible  that  the  whole  series  is  nothing  less  than  a 
demonstration,  in  this  case  at  least,  of  origin  of  species 
by  derivation  with  modifications.  The  accompanying 
plate  of  successive  forms  (Fig.  70),  which  we  take  from 
Prof.  Hyatt's  admirable  memoir,  will  show  this  better 
than  any  mere  verbal  explanation.  It  will  be  observed 
that,  commencing  with  four  slight  varieties — probably 
sexually  isolated  varieties  —  of  one  species,  each  series 
shows  a  gradual  transformation  as  we  go  upward  in  the 
strata — i.  e.,  onward  in  time.  Series  I  branches  into 
three  sub-series,  in  two  of  which  the  change  of  form  is 
extreme.  Series  IV  is  remarkable  for  great  increase  in 
size  as  well  as  change  in  form.  In  the  ]}late  we  give  only 
selected  stages,  but  in  the  fuller  plates  of  the  memoir^ 
and  still  more  in  the  shells  themselves,  the  subtilest  gra- 
dations are  found. 

This  case  is  striking,  partly  because  it  is  a  very  favor- 
able one,  but  mainly  because  it  has  been  so  carefully 
studied.  There  can  be  no  doubt  that  equally  careful 
study  would  reveal  the  same  transition  in  many  other 
cases.  Nor  are  such  transitions  confined  to  the  lower 
forms  of  life,  though  they  are  probably  more  abundant 
there.  According  to  Cope,  the  nicest  gradations  may  be 
traced  between  some  of  the  extinct  mammalian  species 
so  abundant  in  the  Tertiary  deposits  of  the  West — espe- 


238    EVIDENCES   OF   THE   TRUTH   OF   EVOLUTION. 


Fig.  YO. — Transformations  of  Planorbis  (after  Hyatt). 

Soies  IV.     1,  PI.  levis:  Undorf.     2,  PI.  Steinheimensis  ;  3,  tenuis-Stein- 

heimensis ;  4,  tenuis ;  5,  discoicieus  ;  6,  trochiformis-discoideus ;  7, 

trochiformis :  Steinheim. 
Series  III.     8,  PI.  levis:  Undorf.     9,  PI.  oxystomus ;  10,  suprcmus ;  11, 

supremus  var.  turrita  :  Steinheim. 
Series  II.    12,  PI.  levis:  Undorf,      13,  PI. crescens-parvus  ;  14,  15,  cres- 

cens:  Steinheim. 
Series  I.     Sub-series  3.     16,  PI.  levis:  Undorf.     17,  PI.  minutus-levis ; 


PROOFS  FROM  ARTIFICIAL  PRODUCTION.      239 

18,  minutus;  19,  20,  triquetrus :  Steinheira.  Sub-series  2.  21,  PI. 
minutus  ;  22,  28,  denudatus-minutus  ;  24,  denudatus  var.  distortus : 
Steinheim.  Sub-scries  1.  25,  PI.  costatus-minutus  ;  26,  costatus  ; 
27,  28,  costatus  var  —  :  Steinheim. 
The  specimens  from  Undorf  all  belong  to  an  older  Tertiary  period  than 
that  at  Steinheim. 

cially  between  the  species  of  the  extinct  generalized  fam- 
ily of  Oredontidce.'^  The  same  is  probably  true  of  the 
many  extinct  species  of  the  horse  family. 

It  is  interesting  to  observe  that  the  details  of  the  pro- 
cess of  change  in  the  forms  of  Planorhis  are  in  accord 
with  Dr.  Eomanes's  views.  The  change  does  not  seem 
to  have  been  uniform  but  somewhat  paroxysmal.  The 
forms  seem  to  remain  stable  for  a  long  time,  and  then  a 
few  break  into  several  different  forms,  while  the  more 
rigid  die  out.  It  is  as  if  cross-breeding  had  kept  the 
type  true,  but  at  the  same  time  increased  its  tendency  to 
variation,  until  finally  one  or  more  varieties  became  sexu- 
ally isolated  and  thus  formed  new  species. 

5.  But  still  the  question  remains  :  Why  are  transi- 
tional forms  rare  in  all  cases,  esj^ecially  between  species — 
so  rare  that  they  are  eagerly  sought  and  highly  prized  ? 
I  believe  that  the  true  reason  of  this  is  that  the  steps  of 
evolution  are  not  ahvays  uniform. 

Nearly  all  evolutionists  have  assumed  and  even  in- 
sisted on  uniformity,  as  the  opposite  of  catastrophism 
and  of  supernaturalism,  and  therefore  as  essential  to  the 
idea  of  evolution.     They  say  that  the  constancy  of  the 

*  In  a  letter  to  the  author,  dated  February  13,  ISSY,  Prof.  Cope  says : 
"Such  transitions  of  species  are  clearly  indicated  in  the  Oreodontidce, 
where  such  different  forms  as  0.  gracilis  and  0,  Culbertsoni  are  connected 
by  intergradations." 


240    EVIDENCES   OF  THE  TRUTH   OF  EVOLUTION. 

action  of  the  forces  of  change  necessitates  the  uniformity 
of  the  rate  of  change.  But,  in  fact,  this  is  not  always 
nor  even  usually  true.  Causes  or  forces  are  constant,  but 
phenomena  everywhere  and  in  every  department  of  Ma- 
ture are  paroxysmal.  The  forces  producing  storms  and 
lightning,  and  volcanoes  and  earthquakes,  are  or  may  be 
constant ;  yet  the  phenomena  are  in  the  highest  degree 
paroxysmal.  Wherever  in  nature  we  have  a  constant 
force  and  a  strong  resistance,  we  find  more  or  less  parox- 
ysmal action.  For  this  reason  the  wind  blows  in  puffs, 
the  friction  of  wind  on  water  produces  waves,  water  run- 
ning in  small  pipes  issues  in  pulses.  The  reason  is  ob- 
vious, as  may  be  seen  by  the  following  examples  :  Sup- 
pose lifting  forces  witliin  the  earth  are  resisted  by  crust- 
rigidity.  The  forces  accumulate  uniformly  until  the 
resistance  gives  way,  and  suddenly  we  have  an  earth- 
quake. Water  running  with  great  resistance  in  small 
pipes  is  checked,  but  soon  accumulates  additional  force, 
which  overcomes  the  resistance,  only  to  be  again  checked, 
and  so  on,  and  therefore  runs  in  pulses.  Now,  the  course 
of  evolution  of  the  whole  earth  may  be  likened  to  such  a 
current  ;  there  are  forces  of  movement  and  forces  of  re- 
sistance— progressive  forces  and  conservative  forces.  The 
progressive  force  is  accumulative,  the  resisting  force  is 
constant.  Thus,  in  all  evolution  or  history,  whether  of  the 
earth  or  of  society,  there  are  periods  of  comparative  quiet, 
during  which  the  forces  of  change  are  gathering  strength, 
and  periods  of  revolution  or  rapid  change,  during  which 
these  forces  show  themselves  in  conspicuous  effects. 


PROOFS   FROM  ARTIFICIAL  PRODUCTION.      241 

Now,  that  there  have  been  such  periods  of  rapid  revo- 
lutionary change  in  the  history  of  the  earth,  there  can  be 
no  doubt.  The  history  of  the  earth  is  marked  by  periods 
of  comparative  quiet,  during  which  life  was  exception- 
ally abundant  and  jorosperous,  and  change  of  organic 
forms  slow  and  uniform — separated  by  periods  of  dis- 
turbance, revolution,  rapid  changes  of  physical  geogra- 
phy and  climate,  and  consequently  of  comparatively  rapid 
and  sweeping  changes  in  organic  forms.  These  form  the 
division-lines  between  great  eras  of  the  earth's  history, 
and  are  alv/ays  marked  by  extensive  unconformity  of  the 
strata,  showing  the  changes  of  physical  geography  above 
spoken  of,  and  by  apjiarently  sudden  and  sweeping 
change  in  life-forms,  showing  the  great  changes  of  cli- 
mate and  other  physical  conditions.  Unfortunately,  in 
all  cases  of  unconformity  of  strata,  there  is,  of  course,  a 
break  in  the  continuity  of  the  record  ;  and  when  the  un- 
conformity is  very  general  a  portion  of  the  record  may 
be  irrecoverably  lost.  The  consequence  is,  that  there  is 
an  apparent  break  also  in  the  continuity  of  life-forms.  It 
looks,  at  first  sight,  like  wholesale  extermination  of  old 
and  recreation  of  new  forms.  But  undoubtedly  the  break 
in  the  continuity  of  life  is  apparent  only,  as  is  shown  by 
the  loss  in  the  record.  If  we  could  recover  the  whole 
record,  as  indeed  we  sometimes  do,  we  should  find  in  all 
cases  that  there  is  no  break  in  the  continuity  of  evolu- 
tion, but  only  more  rapid  rate  of  change  at  these  times. 
But  to  this  cause  of  rapid  rate  of  j^rogress — i.  e.,  change 
of  physical  environment — we  must  add  change  of  organic 


242    EVIDENCES   OF   THE   TRUTH   OF   EVOLUTIOK 

environment  induced  bj  the  physical.  We  have  already 
seen  (p.  179)  that  extensive  changes  in  physical  geogra- 
phy and  climate  are  always  accompanied  by  wide  migra- 
tions and  dispersals  of  species,  the  mingling  of  faunas 
and  floras,  and  the  severer  struggle  for  life,  and  the 
sweeping  weeding-out  of  all  but  the  fittest,  and  the 
change  of  these  latter,  making  them  still  fitter.  These 
two  causes  of  rsi])\d  change,  viz.,  change  of  climate  and 
migrations,  together  with  the  loss  of  record,  we  believe 
completely  account  for  those  sweeping  changes,  not  only 
of  species  but  even  of  genera,  families,  and  orders  W'hich 
characterize  the  passage  from  one  great  era  to  another. 

But  this  does  not  yet  explain  the  apparent  disconti- 
nuity between  consecutive  sj^ecies  in  the  same  locality  in 
continuous,  conformable  strata,  or  the  rarity  of  transi- 
tional forms  when  one  species  takes  the  place  of  another 
in  an  ajoparently  continuous  record.  In  such  continuous 
deposits  the  successive  faunas  do  indeed  gradate  insensi- 
bly into  one  another,  but  apparently  as  in  contiguous  geo- 
graphical regions  (p.  200)  by  substitution,  not  by  trans- 
mutation.    How  shall  we  explain  this  ? 

On  this  point  I  throw  out  some  suggestions  :  1.  In 
the  modification  of  species,  too,  as  well  as  in  other  pro- 
gressive changes,  we  may  imagine  two  forces  operating, 
one  progressive,  the  other  conservative — tlie  one  external, 
the  other  internal.  The  external  progressive  force  con- 
sists of  all  the  factors  of  change  already  mentioned,  the 
internal  conservative  is  the  law  of  heredity,  of  like  pro- 
ducing like.     A  changing  environment  tends  continually 


PROOFS   FROM   ARTIFICIAL  PRODUCTION".      243 

and  increasingly  to  change  of  organisms,  but  change  is 
resisted  by  heredity,  which  tends  to  adhere,  within  nar- 
row limits,  to  the  same  form.  But  since  the  external- 
force  or  tendency  to  change  increases  constantly — since 
the  discord  between  the  environment  and  the  organism 
becomes  ever  greater,  there  must  come  a  time  when  either 
the  species  is  destroyed,  or  else  the  resistance  of  heredity 
gives  way,  and  rapid  change  takes  place.  The  alternative 
is  presented  to  the  species  to  transform  or  perish  ;  and  in 
one  or  perhaps  in  two  or  three  generations  we  have  an 
amount  of  change  which,  under  other  circumstances, 
might  take  a  hundred  generations  to  accomplish.  These 
rapid  changes  are  in  fact  exactly  what  in  artificial  varie- 
ties we  call  sports.  We  do  not  know  all  the  conditions 
which  determine  sports  in  domestication,  and  still  less 
what  determines  large  and  widely-divergent  variations, 
and  therefore  rapid  origin  of  many  divergent  species,  in 
geological  history.  But  one  thing  seems  probable,  viz., 
that,  when  a  species  begins  to  change,  it  continues  to 
change  easily  and  in  many  directions.  When  resistance 
gives  way  it  takes  some  time,  many  generations,  for  he- 
redity to  gather  force  again.  Hence,  young  species  are 
plastic,  fluent,  because  heredity,  on  any  one  point,  has 
not  yet  accumulated.  But  as  soon  as  a  stable  form  is 
again  reached,  then,  by  accumulating  a  fund  of  heredity, 
the  form  tends  to  become  more  and  more  rigidj  until 
often  it  becomes  too  rigid  to  yield  to  modifying  influ- 
ences, and  therefore  becomes  extinct.  By  far  the  greater 
number  of  species  do  thus  become  extinct  and  leave  no 


24:4:    EVIDENCES   OF  THE  TRUTH   OF  EVOLUTION. 

progeny,  while  the  few  more  plastic  forms  are  modified 
in  several  directions,  and  the  number  of  forms  may,  after 
a  little  time,  be  undiminished  or  even  increased. 

2.  As  to  the  catise  of  rapid  changes  of  form  during 
revolutionary  or  critical  periods  in  the  earth's  history, 
Brooks  has  introduced  an  idea  which  is  very  suggestive, 
and  deserves  serious  attention.  We  have  above  spoken 
of  the  progressive  element  as  external.  Brooks  regards 
both  elements  as  internal,  and  represented  by  the  two 
sexes.  The  male  represents  the  progressive,  the  female 
the  conservative  element.  The  one  tends  to  divergent 
variation,  the  other  to  fixity  of  type  by  heredity.  I 
think  we  will  all  admit  that,  as  a  general  rule,  in  man 
(and  probably  all  the  higher  animals)  the  male  is  more 
highly  differentiated  into  many  divergent  forms  —  the 
female  is  more  like  the  type-form  of  the  species.  In 
man,  the  male  is  certainly  more  diversified  in  form,  in 
expression,  and  in  character.  If  they  have  the  keenest 
ear  for  musical  pitch,  they  are  also  most  often  music- 
deaf  ;  if  they  have  the  sharpest  jDcrception  of  color,  they 
are  also  most  often  color-blind  ;  if  among  them  we  find 
the  brightest  intellects,  we  also  find  the  dullest  and 
most  stupid  ;  if  there  are  among  them  more  geniuses, 
so,  also,  there  are  more  cranks.  The  same  is  also,  prob- 
ably, true  of  other  animals,  in  proportion  to  their  grade 
of  organization.  The  operation  of  these  two  equally 
necessary  elements  is  well  shown  in  every  advancing 
society.  The  initiative  of  every  movement,  in  all  direc- 
tions, good  or  bad,  is  determined  by  the  male  ;  the  con- 


PROOFS  FROM  ARTIFICIAL  PRODUCTION".      245 

servation  of  whateyer  balance  of  good  there  may  be, 
seems  to  be  mainly  by  the  female.  The  male  tries  all 
things,  the  female  holds  fast  that  which  is  good.  By 
the  one  society  gains  a  little  in  each  generation  ;  by  the 
other  the  gain  is  conserved  and  made  a  new  point  of 
departure.  The  one  is  ever  building  hastily  a  scaffold- 
ing and  platform ;  the  other  ever  consolidating  into  a 
permanent  structure.  Now,  according  to  Brooks,  what 
is  true  in  the  plane  of  social  progress  is  true  also  in 
the  lower  plane  of  organic  evolution.  In  sexual  union, 
and  in  the  resulting  offspring,  the  sperm-cell  is  the 
element  which  tends  to  divergent  variation,  and  the 
germ-cell  to  fixity  of  type,  through  heredity.  In  arti- 
ficial breeding,  then,  we  ought  to  make  new  varieties  by 
proper  use  of  the  sire ;  we  ought  to  preserve  them  true 
by  proper  mauagement  of  the  dam. 

But,  again,  it  is  believed  that  in  many  lower  ani- 
mals, especially  insects,  the  high-feeding  of  the  mother, 
and  consequent  good  condition  of  the  ovum,  tends  to 
the  production  of  female  offsjoring.  It  seems  almost 
certain  that,  in  butterflies,  the  sex  is  not  yet  declared 
in  the  caterpillar  stage.  According  to  the  careful  ex- 
periments of  Mrs.  Treat, "^  if  the  caterpillars  be  well  fed, 
they  become  female  butterflies ;  but,  if  poorly  fed,  they 
make  males.  One  purpose  of  this  provision  of  Kature 
is,  doubtless,  to  provide  for  the  greater  draught  on  the 
vitality  of  the  female  in  reproduction. 

*  "American  Naturalist,"  ISYS;  "Popular  Science  Monthly,"  June, 
1873. 


246    EVIDENCES   OF   THE   TRUTH   OF  EVOLUTION. 

'Now  for  the  application.  In  good  times  in  the  his- 
tory of  a  species,  when  everything  is  prosperous,  external 
conditions  are  favorable,  and  food  is  abundant,  females 
are  in  excess,  and  individuals  are  greatly  multiplied. 
Under  these  conditions,  evolution  would  be  slow  and 
uniform.  But  in  Md  times  in  the  history  of  a  species, 
when  external  conditions  were  unfavorable,  not  only 
Vfould  there  be  excess  of  males,  but  these,  through  the 
influence  of  the  changing  environment,  as  well  as  through 
the  dominance  of  the  male  element,  would  be  more  than 
usually  varied  in  character.  Among  the  strongly  diver- 
gent varieties  thus  formed,  the  fittest — i.  e.,  those  most 
in  accord  with  the  changing  environment — would  sur- 
vive and  leave  offsioring  partaking  of  their  character. 
We  have  already  repeatedly  said  that  the  severer  pressure 
of  a  rapidly-changing  environment  determines  corre- 
sjoondingly  rapid  changes  in  organic  forms.  It  may  do 
so  in  many  ways ;  but,  according  to  Brooks,  one  of  the 
most  important  ways  is  by  determining  an  excess  of  the 
male  element. 

In  brief,  then,  the  causes  of  rarity  of  transitional 
forms  among  fossils  are — 1.  The  change  being,  for  the 
reasons  given,  comparatively  rajiid,  the  numher  of  gen- 
erations between  consecutive  species  are  few,  perhaps 
only  one.  2.  Times  of  rapid  change  are  also  times  of 
unfavorable  conditions,  and  therefore  the  number  of 
individuals  in  each  generation  is  small,  and  all  the 
smaller — in  Brooks's  view — because  of  the  fewness  of 
females.      AVhen   we    remember  that  fossils  are  but  a 


PROOFS  FROM  ARTIFICIAL  PRODUCTION.      2iT 

small  fraction  of  the  actual  faunas  and  floras  of  the 
time,  surely  these  two  causes  go  far  toward  explaining 
the  rarity  of  links  between  species.  3.  Add  to  these 
the  existence  of  periods  of  wide-spread  changes  in  physi- 
cal geography  and  climate,  and  consequent  wide  migra- 
tions and  dispersals  of  species,  and  we  sufficiently  ac- 
count for  those  sweeping  changes  in  species,  genera, 
families,  and  orders,  which  mark  the  limits  of  the  great 
eras,  and  which  are  made  still  more  abrupt,  and  appar- 
ently supernatural,  by  the  loss  of  record  at  these  times.* 

Objection. — There  is  still  one  more  objection  which 
will  be  made.  We  have  drawings  of  plants,  animals, 
and  men,  by  Egy2:»tian  artists,  who  lived  at  least  three 
thousand  years  ago,  and  the  species  of  the  one  and  the 
races  of  the  other  are  still  the  same.  Still  better,  we 
have  among  the  wrappings  of  Egyptian  mummies  the 
very  plants  themselves,  leaves  and  flowers  perfectly 
preserved,  and  even  colors  almost  perfect.  Yet  the 
species  are  exactly  the  same  as  grow  in  Egypt  to-day. 
If  species  are  made  by  gradual  transmutation,  surely 
there  ought  to  have  been  some  change  in  three  thou- 
sand years. 

Answer. — It  may  be  well  to  note  that  this  apparent 
permanence  is  true  of  races  of  men  as  well  as  of  spe- 
cies  of   animals   and   plants.      But   the  very  men  who 

*  For  a  fuller  development  of  this  subject  the  reader  is  referred  to 
an  article  by  the  author,  entitled  "  Critical  Periods  in  the  History  of,  and 
thair  Relation  to,  Evolution  "  ("  American  Journal  of  Science,"  vol.  xiv, 
p.  99,  1877). 
12 


248    EVIDENCES   OF  TEE  TRUTH   OF  EVOLUTION". 

insist  on  permanence  of  sj^ecies  are  equally  insistent  on 
the  yariability  of  yarieties  and  races.  The  objection, 
therefore,  proves  too  much.  We  shall  not  insist  on  this, 
however,  because  as  derivationists  we  reirard  races  as 
naught  else  than  commencing  species,  and  therefore 
subject  to  the  same  laws.  We  ai'e  not  striving  for  tri- 
umph in  debate,  but  only  for  truth.  The  true  answer 
will,  we  believe,  be  found  among  the  following  sugges- 
tions : 

1.  Three  thousand  years  seems  a  long  time  in  human 
history,  but  in  geological  history  it  is  but  a  day.  This, 
the  usual  answer,  is  no  doubt  a  true  one,  but  hardly, 
we  think,  sufficient.  When  we  remember  the  enormous 
change  whicli  has  taken  place  in  faunas  and  floras  since 
the  end  of  the  Tertiary,  if  change  still  continues  at  the 
same  rate,  surely  it  ought  to  be  distinctly  perceptible 
in  three  thousand  years. 

2.  But  we  must  remember  that  such  changes  are 
usually  more  or  less  paroxysmal ;  not,  indeed,  so  sud- 
den as  to  break  the  continuity  of  life,  but  far  more 
rapid  at  some  times  than  at  others.  The  last  critical 
or  revolutionary  period  of  rapid  change  was  the  Glacial 
epoch.  Since  that  time — i.  e.,  during  the  human  pe- 
riod— a  new  equilibrium  has  been  established,  and  the 
changes  in  organic  forms  have  been  very  slow. 

3.  Remember,  again,  that  in  evolution  all  sjiecies 
do  not  change.  On  the  contrary,  most  become  rigid, 
and  either  remain  unchanged,  almost  indefinitely,  or 
else  die  out  and  leave  no  descendants.     Only  the  more 


PROOFS  FROM  ARTIFICIAL  PRODUCTION.      249 

plastic  forms  change  into  other  species,  but  usually 
into  several  other  s^DCcies,  and  thus  the  number  of  forms 
may  be  undiminished,  even  though  the  larger  number 
of  old  forms  leave  no  descendants.  It  is  true,  there- 
fore, of  this  as  well  as  of  other  epochs,  that  the  greater 
number  of  species  are  permanent. 

4.  It  is  not  impossible — indeed,  it  is  in  exact  ac- 
cordance v\^ith  the  laws  of  evolution — that  organic  forms 
are  more  permanent  now  than  ever  before.  Evolution 
is  a  growth  ;  the  forces  of  growth  must  exhaust  them- 
selves. Evolution  proceeds  by  constant  differentiation 
and  specialization,  but  extreme  specialization  always 
arrests  evolution.  In  ontogenic  evolution,  for  example, 
cell-structure  becomes  more  and  more  specialized,  but 
also  thereby  more  and  more  rigid,  and,  when  special- 
ization is  complete,  evolution  stops,  and  cell-forms  are 
permanent.  It  is  this  which  limits  the  cycle  of  every 
evolution.  So  is  it  precisely  wdth  evolution  of  the  or- 
ganic kingdom,  except  that  the  cycle  is  much  longer. 
Here,  also,  every  step  is  by  specialization,  and  yet  spe- 
cialization fixes  the  form,  and  finally  arrests  the  advance 
on  that  line.  Thus,  throughout  the  whole  geological 
history  of  the  earth,  the  larger  number  of  forms,  by 
specialization,  become  rigid  and  perish,  while  the  fewer, 
more  generalized,  and  more  plastic  forms  take  up  the 
march  and  carry  it  forward  a  step,  only  to  be  them- 
selves specialized  and  fixed.  If  we  compare,  again,  to  a 
tree  :  each  twig  finishes  its  growth,  flowers,  fruits,  and 
dies  ;  other  buds  take  up  the  grow^tli  and  carry  it  for- 


250    EVIDENCES   OF  THE   TRUTH   OF  EVOLUTION. 

ward.  By  specialization  the  highest  condition  of  a  cer- 
tain form  of  life  is  attained,  but  other  possibilities  are 
shut  off.  Extreme  specialization  is  the  flowering  and 
fruiting — the  end  and  completion  of  twig-life.  ISTow, 
obviously,  this  specialization  and  respecialization  can 
not  go  on  forever.  When  it  is  complete  in  every  direc- 
tion it  must  cease,  and  forms  become  permanent,  or  else 
perish.     When  it  flowers  it  must  die. 

Now,  is  not  the  advent  of  man  in  many  ways  a  sign 
of  the  completeness  of  organic  evolution  ?  Certain  it 
is  that  with  man  there  begins  an  entirely  new  form  of 
evolution.  Certain  it  is  that  with  man  evolution  is 
transferred  from  the  organic  to  the  social  plane,  from 
the  material  to  the  psychical.  Certain  it  is  that  the 
forces,  the  conditions  and  results  of  this  evolution,  are 
wholly  different  from  those  of  the  other.  In  organic  evo- 
lution the  organism  must  conform  to  the  environment ; 
in  human  evolution  the  environment  is  made  to  conform 
to  the  wants  of  the  organism.  The  one  is  unconscious 
and  involuntary,  passive  under  the  dominating  laws  of 
Nature  ;  the  other  is  conscious,  voluntary  progress  toward 
an  ideal,  ly  the  use,  among  other  means,  of  the  laws  of 
Nature.  The  one  is  by  change  of  external  form — i.  e., 
change  of  species — the  other  by  change  of  brain-struct- 
ure. Now,  does  not  the  commencing  of  the  cycle  of 
this  new  evolution  imply  the  closing  of  that  of  the  old  ? 
The  two  may  overlap  somewhat  now,  but  it  is  evident 
that,  when  the  cycle  of  human  evolution  culminates, 
when  highly  civilized  man  shall  have  taken  possession 


PROOFS  FROM  ARTIFICIAL  PEODUCTIOX.      251 

of  the  whole  earth,  the  whole  organic  kingdom  must 
be  readjusted  to  his  wants.  All  organic  forms  must  be 
either  domesticated  or  destroyed.  Organic  forms  will 
no  longer  be  modified  by  natural  but  wholly  by  arti- 
ficial selection. 

There  are  many  other  supposed  objections  which  have 
been  urged,  but  these  are  mostly  not  objections  to  evo- 
lution, but  only  to  some  special  theory  of  CTolution — 
Darwinian,  Spencerian,  Lamarckian,  or  other. 

Origin  of  Beauty. — For  example,  it  has  been  urged 
that  natural  selection  can  only  account  for  useful  struct- 
ures ;  but  'beauty  is  as  universal  and  as  conspicuous  in 
nature  as  use.  In  many  cases  Darwin  has  shown  that 
beauty  is  useful,  and  in  such  cases  it  is,  of  course, 
seized  upon  by  selection  and  intensified.  Thus,  the 
gorgeous  coloring  of  birds  and  insects  is  largely  due 
to  sexual  selection.  Beauty  is  attractive,  and  therefore 
the  most  beautiful  i^revail  in  securing  reproductive  op- 
portunities. This  character  is,  therefore,  perpetuated 
in  the  offspring,  and  intensified  from  generation  to  gen- 
eration. But,  of  course,  this  can  apply  only  to  higher 
animals,  in  which  the  sexes  are  separate  and  sexual 
union  voluntary.  It  can  not  apply  to  self-fertilizing 
hermaphrodites  ;  and  yet  in  these,  also,  we  often  find 
the  most  gorgeous  coloring.  Again,  Darwin  has  very 
ingeniously  and  successfully  exi^lained  the  case  of  the 
beauty  and  fragrance  of  flowers  of  hermaphroditic  plants 
by  another  principle,  viz.,  that  of  insect-selection.     In- 


252    EVIDENCES   OF  THE   TRUTH    OF   EVOLUTION. 

sects  are  attracted  by  the  most  showy  and  fragrant 
flowers,  and  thus  become  the  means  of  carrying  i:»ollen 
from  flower  to  flower,  insuring  fertilization,  and  espe- 
cially cross-fertilization.  The  most  beautiful  and  fra- 
grant flowers  are  most  certain  to  be  fertilized,  and  tiuis 
beauty  and  fragrance  become  useful  to  the  jilant,  and 
therefore  are  selected  and  intensified. 

These  and  many  other  cases  of  beauty  may  doubtless 
be  explained  by  showing  that  it  is  useful  ;  but  beauty 
wliich  is  without  any  use  can  not  be  exjilained  by  nat- 
ural selection.  Xow,  as  already  said,  the  most  gorgeous 
beauty  is  lavishlv  distributed  even  among  the  lowest 
animals,  such  as  marine  shells  and  pol3'p3,  where  no  such 
exj^lanatiou  is  possible.  The  process  by  which  such 
beauty  is  originated  and  intensified  is  wholly  unknown 
to  us. 

Incipient  Organs. — Again,  Mivart  has  drawn  attention 
to  another  difficulty  in  the  way  of  natural  selection  as  an 
explanation  even  of  useful  organs.  Darwin  does  not,  of 
course,  attempt  to  account  for  the  origin  of  varieties. 
As  we  have  already  seen,  he  assumes  diyer£:ent  variation 
of  offspring  as  the  necessary  material  on  which  natural 
selection  operates.  He  who  shall  explain  the  origin  of 
yarieties  will  have  made  another  great  step  in  completing 
the  theory  of  evolution.  But  not  only  does  not  natural 
selection  explain  the  origin  of  varieties,  but  neither  can 
it  explain  the  first  steps  of  advance  toward  usefulness. 
An  organ  n-iust  be  already  useful  before  natural  selection 
can  take  hold  of  it  to  improve  it.     It  can  not  make  it 


PROOFS  FROM  ARTIFICIAL  PRODUCTION".      253 

useful,  but  only  more  useful.  For  example,  if  fins  com- 
menced as  buds  from  the  trunk,  it  is  difficult  to  see  hoAv 
they  could  be  of  any  use,  and  therefore  how  they  could 
be  improved  by  natural  selection  until  they  were  of  con- 
siderable size,  and  especially  until  muscles  were  developed 
to  move  them.  Until  that  time  they  would  be  a  hin- 
drance to  be  removed  by  natural  selection,  instead  of  a 
use  to  be  preserved  and  improved.  It  would  seem  that 
all  organs  must  have  passed  through  this  incipient  stage, 
in  which  their  use  was  prospective. 

Much  that  is  very  interesting  might  be  said  on  these 
and  similar  points  of  difficulty,  but  all  this  lies  entirely 
aside  from  the  scope  of  this  work.  As  already  said,  these 
are  not  objections  to  evolution  or  derivation,  but  only 
to  Darivinism,  or  any  other  special  theory,  as  a  sufficient 
exiiilanation  of  the  process  of  evolution.  They  only  show 
that  we  do  not  yet  fully  understand  this  process ;  that 
there  are  still  other  and  perhaps  greater  factors  of  evolu- 
tion than  is  yet  dreamed  of  in  our  philosophy. 

In  the  foregoing  chapters  on  special  evidences,  and 
especially  in  the  last  two,  the  reader  will  observe  many 
points  of  doubt,  discussion,  and  difference  of  opinion. 
Let  it  not  be  concluded  on  that  account  that  the  laic  of 
evolution  is  still  in  the  region  of  uncertainty.  It  can 
not  be  too  strongly  insisted  on  that  the  fact  of  evolution 
as  a  universal  law  must  be  kept  distinct  from  the  causes, 
the  factors,  the  conditions,  the  processes,  of  evolution. 
The  former  is  certain,  the  latter  are  still  imperfectly  un- 
derstood. 


P  AET     III. 

THE  RELATION  OF  EVOLUTION  TO 

RELIGIOUS   THOUGHT. 


CHAPTER  L 

IN^TRODUCTORY. 

From  what  has  preceded,  the  reader  will  i^erceive 
that  we  regard  the  law  of  evolution  as  thoroughly  estab- 
lished. In  its  most  general  sense,  i.  e.,  as  a  law  of  con- 
tinuity, it  is  a  necessary  condition  of  rational  thought. 
In  this  sense  it  is  naught  else  than  the  universal  law  of 
necessary  causation  applied  to  forms  instead  of  phe- 
nomena. It  is  not  only  as  certain  as — it  is  far  more 
certain  than — the  law  of  gravitation,  for  it  is  not  a  con- 
tingent, but  a  necessary  truth  like  the  axioms  of  geome- 
try. It  is  only  necessary  to  conceive  it  clearly,  to  accept 
it  unhesitatingly.  The  consensus  of  scientific  and  phil- 
osophical opinion  is  already  well-nigh,  if  not  wholl}^, 
complete.  If  there  are  still  lingering  cases  of  dissent 
among  thinking  men,  it  is  only  because  such  do  not  yet 
conceive  it  clearly — they  confound  it  with  some  special 
form  of  explanation  of  evolution  which  they,  perhaps 
justly,  think  not  yet  fully  established.  We  have  some- 
times in  the  preceding  pages  used  the  words  evolutionist 
or  derivationist ;  they  ought  not  to  be  used  any  longer. 
Tlie  day  is  past  when  evolution  might  be  regarded  as  a 


258      EVOLUTION   x\ND  RELIGIOUS  THOUGHT. 

school  of  thought.     "We  might   as  well  talk  of  gravita- 
tionist  as  of  evolutionist. 

If,  then,  evolution  as  a  law  be  certain,  if,  moreover, 
it  is  a  law  affecting  not  only  one  part  of  Nature — the 
organic  kingdom — and  one  department  of  science — bio- 
logy— but  the  whole  realm  of  Nature  and  every  depart- 
ment of  science,  yea,  every  department  of  thought, 
changing  our  whole  view  of  Nature  and  modifying  our 
whole  philosophy,  the  question  presses  ujion  us,  ^'  What 
will  be  its  effect  on  religious  belief,  and  therefore  on 
moral  conduct  ?  "  This  is  a  question  of  gravest  import. 
To  answer  it,  however  imperfectly,  is  the  chief  object  of 
this  work.  Except  for  this,  it  would  probably  never 
have  been  undertaken.  All  that  goes  before  is  sub- 
sidiary to  this. 

But  I  will  doubtless  be  met  at  the  very  threshold  by 
an  objection  from  the  scientific  side.  Some  will  say — 
because  it  is  the  fashion  now  to  say — that  as  simple, 
honest  truth-seekers,  we  have  nothing  to  do  with  its 
effect  on  religion  and  on  life.  They  say  we  must  follow 
Truth  wherever  she  leads,  utterly  regardless  of  what  may 
seem  to  us  moral  consequences.  This  I  believe  is  a  grave 
mistake,  the  result  of  a  reaction,  and  on  the  whole  a 
wholesome  and  noble  reaction,  against  the  far  more  com- 
mon mistake  of  sacrificing  truth  to  a  supposed  good. 
But  the  reaction,  as  in  most  other  cases,  has  gone  much 
too  far.  There  is  a  true  philosophic  ground  of  justifica- 
tion for  the  reluctance  with  w^hich  even  honest  truth- 
seekers  accept  a   doctrine  which  seems  harmful  to   so- 


INTRODUCTORY.  259 

ciefcy.  Effect  on  life  is,  and  ought  to  be,  an  important 
element  in  our  estimate  of  the  truth  of  any  doctrine.  It 
is  necessary  for  me  to  show  this,  in  order  to  justify  this 
part  of  my  work. 

Relation  of  the  True  and  the  Good. — There  is  a  ne- 
cessary and  indissolnble  connection  between  truth  and 
usefulness.  We  all  at  once  admit  this  connection  in  one 
direction.  We  all  admit  that  a  truth  must  eyentually 
have  its  useful  application.  It  may  not  be  noiv,  nor  in 
ten  years,  nor  in  a  century,  nor  even  in  a  millennium, 
but  some  time  in  the  future  it  will  vindicate  its  useful- 
ness. No  truth  is  trivial  or  useless  in  its  relation  to 
human  life,  for  man  is  a  part  of  Nature,  and  his  life  must 
be  in  accordance  with  the  laws  of  Nature.  Every  one 
admits  this,  but  not  every  one  admits  the  converge 
proposition,  viz.,  that  whatever  doctrine  or  belief,  in  the 
long  run  and  throughout  the  history  of  human  advance- 
ment, has  tended  to  the  betterment  of  our  race,  must 
have  in  it  an  element  of  truth  by  virtue  of  which  it  has 
been  useful ;  for  man's  good  can  not  be  in  conflict  with 
the  laws  of  Nature.  Also,  vvhatever  in  the  long  run  and 
in  the  final  outcome  tends  to  the  bad  in  human  conduct, 
ought  to  be  received,  even  by  the  honest  trnth-seeker, 
with  distrust  as  containinar  essential  error.  The  reason 
of  this  will  now  be  further  explained. 

Relation  of  Philosophy  to  Life.— There  are  three  pri- 
mary divisions  of  our  psychical  nature,  viz.,  sensuous, 
intellectual,  and  volitional  or  moral.  There  are  three 
corresponding   primary  processes   necessary   to   make   a 


2G0       EVOLUTIOi^  AND   RELIGIOUS   THOUGHT. 

complete  rational  and  satisfactory  philosophy  :  (1)  There 
is  first  the  instreamiiig  of  the  external  world  through  the 
senses,  as  impressions.  These  we  call  facts  or  phenome- 
na. (2)  The  elaboration  of  these  facts  within,  by  the  i7i- 
tellect,  into  a  compact,  consistent  structure.  This  we  call 
knowledge.  (3)  The  outgoing  of  this  knowledge  by  the 
luill  into  the  world  as  ri^ht  or  wise  conduct.  Now  these 
three  are  all  equally  necessary.  All  these  three  portions 
of  our  complex  nature  are  equally  urgent  to  be  satisfied.* 
But,  unfortunately,  scientific  workers  are  too  apt  to 
think  only  1  and  2  necessary — that  true  facts  elaborated 
into  consistent  theory  are  all  we  need  care  for.  Theo- 
logians and  metaphysicians,  on  the  other  hand,  seem  to 
think  only  2  and  3  necessary.  They  elaborate  a  theory 
consistent  in  all  its  parts,  exquisitely  woven  in  beautiful 
and  delicate  pattern,  and  apjiarently  satisfactory  in  its 
aj^plication  to  the  right  conduct  of  life,  but  are  less 
careful  to  inquire  whether  it  is  in  harmony  with  facts 
derived  from  the  senses.  But,  we  repeat,  all  three  are 
equally  necessar}^  The  first  gathers  the  materials,  the 
second  constructs  the  edifice,  the  third,  by  use,  by  prac- 
tical application,  tests  whether  it  be  a  fit  building  to  live 
in,  whether  it  is  constructed  on  sound  architectural  prin- 
ciples. The  tendency  of  the  olden  time  was  to  neglect 
the  first,  the  tendency  of  the  present  time  is  to  neglect 
the  third.  But  we  repeat  with  stronger  emphasis  that  this 
third  element  is  equally  necessary.     All  admit  that  suc- 

*  ''  Reflex  Action  and  Theism,"  William  James,  "  Unitarian  Review  " 
fov  November,  1881. 


INTRODUCTORY.  2G1 

cessful  application  in  art  is  tlie  surest  test  of  the  truth 
of  science.  Now,  social  conduct  is  the  art  correspond- 
ing to  our  philosophy  of  life,  aud  therefore  is  the  sure 
test  of  its  truth.  It  follows,  therefore,  that  unless  all 
these  three  primary  divisions  of  our  nature  are  satis- 
fied by  any  doctrine,  there  must  result  an  ineradicable 
confusion  and  discord  in  our  psychical  nature,  and  cor- 
dial acceptance  is  not  only  impossible  but  irrational. 
We  insist  ujion  this  the  more  because  it  has  become  the 
fashion  in  these  latter  days  of  dominance  of  science,  to 
say  that  to  inquire  into  effects  on  society  is  inconsistent 
with  the  scientific  spirit,  and  unworthy  of  the  honest 
truth-seeker.  But,  observe,  I  am  speaking  of  effects  on 
society  only  as  a  test  of  truth.  I  would  not  swerve  a 
hair's  breadth  from  absolute  devotion  to  truth.  It  is 
necessary,  indeed,  to  inquire  into  effects  on  society,  but 
we  must  inquire  only  in  the  patient  spirit  characteristic 
of  the  truth-seeker.  Whatever  is  really  true  will  surely 
vindicate  itself  by  its  beneficence,  if  we  will  only  wait 
patiently  for  final  results.  Evolution  is  no  exception 
to  this  universal  truth.  It  will  surely  vindicate  its 
beneficence,  but  we  must  wait  yet  a  little  while — not  very 
long. 

So  much  it  was  necessary  to  say  in  justification  of  the 
inquiry  which  constitutes  this  third  part  of  our  work. 
But,  after  this  justification,  the  question  returns  with 
additional  emphasis,  '^  What  will  be  the  effect  of  the 
universal  acceptance  of  the  law  of  evolution  on  religious 
thought,  and  through  this  on  the  right  conduct  of  life  ?" 


282       EVOLUTION   AND   RELIGIOUS   THOUGHT. 

There  can  be  no  doubt  that  evolution,  as  a  law  affect- 
ing all  science  and  every  department  of  Nature,  must 
fundamentally  affect  the  whole  realm  of  thought,  and  pro- 
foundly modify  our  traditional  views  of  JNature,  of  God, 
and  of  man.  There  can  be  no  doubt  that  we  are  now  on 
the  eve  of  a  great  revolution.  But,  as  in  all  great  revo- 
lutions, so  in  this,  the  first  fears  as  to  its  effects  are 
greatly  exaggerated.  To  many,  both  friends  and  foes  of 
Christianity,  evolution  seems  to  sweep  away  the  whole 
foundation,  not  only  of  Christianity,  but  of  all  religion 
and  morals,  by  demonstrating  a  universal  materialism. 
Many  are  ready  to  cry  out  in  anguish,  '^Ye  have  taken 
away  our  gods,  what  have  we  more  ?  Ye  have  destroyed 
our  dearest  hopes  and  noblest  aspirations,  what  more 
is  left  worth  living  for  ?"  But  I  think  all  who  are  at  all 
familiar  with  the  historv  of  the  so-called  conflict  between 
religion  and  science  will  admit  this  is  not  Ihe  first  time 
this  cry  has  been  raised  against  science.  They  have 
heard  this  danger-cry  so  often  that  they  begin  to  regard 
it  as  little  more  than  a  wolf-cry — scientiflc  wolf  in  the 
religious  fold.  It  may  not  be  amiss,  then,  to  stop  a  mo- 
ment to  trace  rapidly  the  main  j^oints  of  this  conflict — to 
discuss  the  various  forms  of  this  scientific  wolf. 

First,  then,  it  came  in  the  form  of  the  heliocentric 
theory  of  the  ^axiMury_siistem.  We  once  thought  the 
earth  the  center  of  the  universe,  and  so  firm  that  it  can 
not  be  moved.  But  science  shows  that  it  moves  about 
the  sun,  and  spins  unceasingly  on  its  axis.  Every  one 
has  heard  of  the  terror  of  the  sheep  produced  by  this  dis- 


INTRODUCTORY.  .  263 

covery,  and  the  nearly  tragic  results  to  the  bold  scientist. 
But  now  we  look  back  with  wonder  that  there  should 
have  been  any  trouble  at  all.  Would  any  Christian  now 
consent  to  give  up  the  grand  conceptions  of  Nature  and 
of  God  thus  opened  to  the  human  mind — the  idea  of 
infinite  space  full  of  worlds,  of  which  our  earth  is  one, 
moving  in  silent  harmony  as  in  a  mystic  dance  ?  Verily, 
this  wolf  has  23roved  itself  a  harmless,  nay,  a  very  noble 
beast,  and  lies  down  in  peace  with  the  lambs. 

l^ext,  it  came  in  the  shape  of  the  law  of  gravitation, 
as  sustentation  of  the  cosmos  by  law  and  resident  forces. 
The  effect  of  this  on  religious  thought  was  even  more 
profound,  though  less  visible  on  the  surface,  because  only 
perceived  by  the  most  intelligent.  It  seemed  at  that  time 
to  remove  God  from  the  course  of  Nature.  This  was  the 
real  ground  of  the  skepticism  of  the  last  century,  and 
also  the  real  motive  of  Voltaire's  ardent  advocacy  of 
Newton's  views  before  these  were  generally  accepted  in 
France.  But  now,  who  would  give  up  this  grand  idea — 
this  conception  of  law  pervading  infinite  space — the  same 
law  which  controls  the  falling  of  a  stone  guiding  also  the 
planetary  orbs  in  their  fiery  courses  ?  This  is  indeed  the 
divine  spheral  music,  inaudible  but  to  the  ear  of  science, 
accompanying  the  celestial  dance. 

Next,  it  came  in  the  form  of  the  antiquity  of  tlie  earth 
and  of  the  cosmos.  The  earth  which  we  had  fondly 
thouglit  made  specially  for  us  about  six  thousand  years 
ago  ;  sun,  moon,  and  stars,  which  we  had  vainly  imagined 
shone  only  for  our  behoof — these,  science  tells  us,  existed 


2G4    eyolutio:n'  and  religious  thought. 

and  each  performed  its  due  course  inconceivable  ages 
before  there  was  a  man  to  till  the  ground  or  contemplate 
the  heavens.  Some  of  my  readers  may  still  remember 
the  horror,  the  angry  disjjute  which  followed  the  pro- 
mulgation of  these  facts.  But  now,  who  would  consent 
to  give  up  the  noble  conception  of  infinite  time  thus 
opened  to  the  human  mind  and  become  forever  the  heri- 
tage of  man  ? 

Next,  it  came  in  the  form  of  the  antiquity  of  man. 

It  is  probable,  na}^,  certain,  that  man  has  inhabited  the 

earth  far  longer  than  we  had  previously  supposed  we  had 
warrant  for  believing.  The  controversy  on  this  question 
and  the  dread  of  its  result  has  indeed  not  yet  entirely 
subsided.  Some  timid  people  still  look  askance  at  this 
wolf,  but  I  think  all  intelligent  people  accept  it  and  find 
it  harmless. 

Next,  and  last,  it  comes  now  in  the  form  of  evolution 
— of  the  origin  of  all  things,  even  of  organic  forms,  by  de- 
rivation— of  creation  hy  law.  AVe  are  even  now  in  the 
midst  of  the  terror  created  by  this  doctrine.  But  what 
is  CA^olution  but  law  throughout  infinite  time  ?  The  _ 
same  law  which  now  controls  the  development  of  an  egg 
.has  presided  over  the  creation  of  worlds.  Infinite  space 
and  the  universal  law  of  gravitation  ;  infinite  time  and  the 
universal  law  of  CYolution.  These  two  are  the  grandest 
ideas  in  the  realm  of  thought.  The  one  is  universal  sus- 
tcntation,  the  other  universal  creation,  by  law.  There 
is  one  law  and  one  energy  pervading  all  space  and  stretch- 
ing through  all  time.     Our  religious  philosophy  has  long 


INTRODUCTORY.  2G5 

ago  accepted  the  one,  but  has  not  yet  had  time  to  re- 
adjust itself  completely  to  the  other.  A  few  more  years, 
and  Christians  will  not  only  accept,  but  love  and  cherish 
this  also  for  the  noble  conceptions  it  gives  of  Nature  and 
of  God. 

But  some  will  exclaim,  '"  Noble  conceptions  of  God, 
say  you  I  Why,  it  utterly  obliterates  the  idea  of  God 
from  the  mind.  All  other  conflicts  were  for  outworks^ 
this  strikes  at  the  citadel.  All  others  required  only  re- 
adjustment of  claims,  rectification  of  bounda^'ies  betwixt 
science  and  religion — this  requires  nothing  less  than  un- 
conditional surrender.  Evolution  is  absolute  material- 
asm,  and  materialism  is  incompatible  with  belief  in  Qod, 
and  therefore  with  religion  of  any  kind  whatsoever  ! " 
Before  proceeding  any  further,  it  becomes  necessary  to 
remove  this  difficulty  out  of  the  way. 


CHAPTER  II. 

THE   EELATIOiT   OF   EYOLUTIOi^   TO   MATERIALISM. 

It  is  seen  in  the  sketch  given  in  the  previous  chapter 
that,  after  eyery  struggle  between  theology  and  science, 
there  has  been  a  readjustment  of  some  beliefs,  a  giving 
up  of  some  notions  which  really  had  nothing  to  do  with 
religion  in  a  proper  sense,  but  which  had  become  so 
associated  with  religious  belief  as  be  to  confounded  with 
the  latter — a  giving  up  of  some  line  of  defense  which 
ought  never  to  have  been  held  because  not  within  the 
rightful  domain  of  theology  at  all.  Until  the  present 
the  whole  difficulty  has  been  the  result  of  misconception, 
and  Christianity  has  emerged  from  every  struggle  only 
strengthened  and  purified,  by  casting  off  an  obstructing 
shell  which  hindered  its  growth.  But  the  present  strug- 
gle seems  to  many  an  entirely  different  and  far  more 
serious  matter.     To  many  it  seems  no  longfer  a  struirsrle 

o  CO 

of  theology,  but  of  essential  religion  itself — a  deadly 
life-and-death  struggle  between  religion  and  materialism. 
To  many,  both  skeptics  and  Christians,  evolution  seems 
to  be  synonymous  with  blank  materialism,  and  therefore 
cuts  up  by  the  roots  every  form  of  religion  by  denying 


RELATION   OF  EVOLUTION  TO   MxVTERIALISM.  267 


the  existence  of  GodanTthe  fact  of  immortality.     That. 
the  enemies  of   religion,  if   there   be   any^such,  should_ 
assume  and  insist  on  this  identity,  and  thus  carry  over 
the  whole  accumulated  eyidence  of  eyolutionliTaT  dem~ 
onstration  of  materialism,  although  wholly  unwarrant- 
ed, is  not  so  surprising ;  but  what  shall  we  say  of  the 
incredible   folly  of   her  friends  in   admitting  the  same 

identity ! 

A  little  reflection  w411  explain  this.  There  can  be  no 
doubt  that  there  is  at  present  a  strong  and  to  many  an 
oyerwhelming  tendency  toward  materialism.  ,^The  amaz- 
ing achieyements  of  modern  science  ;  the  absorj)tion  of 
intellectual  energy  in  the  inyestigation  of  external  nature 
and  the  laws  of  matter  have  created  a  current  in  that  di- 
rection so  strousf  that  of  those  Avho  feel  its  influence — of 
those  who  do  not  stay  at  home,  shut  u]i  in  their  creeds, 
but  walk  abroad  in  the  light  of  modern  thought— it 
sweeps  away  and  bears  on  its  bosom  all  but  the  strongest 
and  most  reflectiye  minds.  Materialism  has  thus  become 
a  fashion  of  thought;  and,  like  all  fashions,  must  be 
guarded  against.  This  tendency  has  been  created  and 
is  now  guided  by  science.  Just  at  this  time  it  is  strong- 
est in  the  department  of  biology,  and  especially  is  eyo- 
lution  its  stronghold.  This  theory  is  supposed  by  many 
to  be  simply  demonstratiye  of  materialism.  Once  it  was 
the  theory  of  gravitation  which  seemed  demonstratiye  of 
materialism.  The  sustentation  of  the  universe  by  law 
seemed  to  imply  that  Nature  operates  itself  and  needs  no 
God.     That  time  is  passed.     Now  it  is  evolution  and 


268       EVOLUTION   AND   RELIGIOUS  THOUGHT. 

creation  by  law.  This  will  also  pass.  The  theory  seems 
to  many  the  most  materialistic  of  all  scientific  doctrine 
only  because  it  is  the  last  which  is  claimed  by  material- 
ism, and  the  absurdity  of  the  claim  is  not  yet  made 
clear  to  many. 

The  truth  is,  there  is  no  such  necessary  connection 
between  evolution  and  materialism  as  is  imagined  by 
some.  There  is  no  difference  in  this  respect  between 
evolution  and  any  other  law  of  Nature.  In  evolution,  it 
is  true,  the  last  barrier  is  broken  down,  and  the  whole 
domam  of  nature  is  now  subject  to  law  ;  but  it  is  only 
the  last ;  the  march  of  science  has  been  in  the  same  di- 
rection all  the  time.  In  a  word,  evolution  is  not  only 
not  identical  with  materialism,  but,  to  the  deep  thinker, 
it  has  not  added  a  feather's  weight  to  its  lorobability  or 
reasonableness.  Evolution  is  one  thing  and  materialism 
quite  another.  The  one  is  an  established  law  of  na- 
ture, the  other  an  unwarranted  and  hasty  inference  from 
that  law.  Let  no  one  imagine,  as  he  is  conducted  by 
the  materialistic  scientist  in  the  paths  of  evolution  from 
the  inorganic  to  the  organic,  from  the  organic  to  the 
animate,  from  the  animate  to  the  rational  and  moral, 
until  he  lands,  as  it  seems  to  him,  logically  and  inevita- 
bly, in  universal  materialism — let  no  such  one  imagine 
that  he  has  walked  all  the  way  in  the  domain  of  science. 
He  has  stepped  across  the  boundary  into  the  domain  of 
philosophy.  But,  on  account  of  the  strong  tendency  to 
materialism  and  the  skillful  guidance  of  his  leaders, 
there  seems  to  be  no   such  boundary ;  he  does  not  dis- 


RELATION   OF  EVOLUTION   TO   MATERIALISM.  2G9 

tino-uish  between  the  inductions  of  science  and  tlie  in- 
ferences  of  a  shallow  philosophy  ;  the  w^hole  is  accredited 
to  science,  and  the  final  conclusion  seems  to  carry  with 
it  all  the  certainty  wdiich  belongs  to  scientific  results. 
The  fact  that  these  materialistic  conclusions  are  reached 
by  some  of  the  foremost  scientists  of  the  present  day 
adds  nothing  to  their  probability.  In  a  question  of  sci- 
ence, viz.,  the  law  of  evolution,  their  authority  is  de- 
servedly high,  but  in  a  question  of  philosophy,  viz., 
materialism,  it  is  far  otherwise.  If  the  pure  scientists 
smile  when  theological  philosophers,  unacquainted  with 
the  methods  of  science,  undertake  to  dogmatize  on  the 
subject  of  evolution,  they  must  pardon  the  philosophers 
if  they  also  smile  when  the  pure  scientists  imagine  that 
they  can  at  once  solve  questions  in  philosophy  which 
have  agitated  the  human  mind  from  the  earliest  times. 
I  am  anxious  to  show  the  absurdity  of  this  materialistic 
conclusion,  but  I  shall  try  to  do  so,  not  by  any  labored 
argument,  but  by  a  few  simple  illustrations. 

1.  It  is  curious  to  observe  how,  when  the  question 
is  concerning  a  work  of  Nature,  we  no  sooner  find  out 
how  a  thino^  is  made  than  w^e  immediatelv  exclaim  :  "  It 
is  not  made  at  all,  it  became  so  of  itself  ! "  So  long  as 
we  knew  not  how  worlds  were  made,  we  of  course  con- 
cluded they  must  have  been  created,  but  so  soon  as  sci- 
ence showed  Jioto  it  was  probably  done,  immediately  we 
say  we  wTre  mistaken — they  were  not  made  at  all.  So 
also,  so  long  as  we  could  not  imagine  how  new  organic 
forms  originated,  we  were  willing  to  believe  they  were 


270       EVOLUTIOX  AND   RELIGIOUS  THOUGHT. 

created,  but,  so  soon  as  we  find  that  they  originated  by 
evolution,  many  at  once  say,  ^^We  were  mistaken;  no 
creator  is  necessary  at  all."  Is  this  so  when  the  question 
is  concerning  a  work  of  man  ?  Yes,  of  one  kind — viz., 
the  work  of  the  magician.  Here,  indeed,  we  believe  in 
him,  and  are  delighted  with  his  work,  until  we  know 
how  it  is  done,  and  then  all  our  faith  and  wonder  cease. 
But  in  any  honest  work  it  is  not  so  ;  but,  on  the  con- 
trary, when  we  understand  how  it  is  done,  stupid  wonder 
is  changed  into  intellectual  delight.  Does  it  not  seem, 
then,  that  to  most  peojole  God  is  a  mere  wonder-worker, 
a  chief  magician.  But  the  mission  of  science  is  to  showjp 
us  how  things  are  done.  Is  it  any  wonder,  then,  that  to 
such  persons  science  is  constantly  destroying  their  super- 
stitious illusions  ?  But  if  God  is  an  honest  worker,  ac- 
cording to  reason — i.  e.,  accordinsr  to  law  —  ouo-ht  not 
science  rather  to  change  ga2:)ing  wonder  into  intelligent 
delight — superstition  into  rational  worship  ? 

2.  Again,  it  is  curious  to  observe  how  an  old  truth, 
if  it  come  only  in  a  neio  form,  often  strikes  us  as  some- 
thing unheard  of,  and  even  as  paradoxical  and  almost 
impossible.  A  little  over  thirty  years  ago  a  little  philo- 
sojihical  toy,  the  gyroscope,  was  introduced  and  became 
very  common.  At  first  sight,  it  seems  to  violate  all  me- 
chanical laws,  and  set  at  naught  the  law  of  gravitation 
itself.  A  heavy  brass  wheel,  four  to  five  inches  in  diame- 
ter, at  the  end  of  a  horizontal  axle,  six  or  eight  inches 
long,  is  set  rotating  rapidly,  and  then  the  free  end  of  the 
axis  is  supported  by  a  string  or  otherwise.    The  wheel  re- 


EELATIOX  OF   EVOLUTION   TO  MATERLVLISM.  071 

mains  suspended  in  the  air  while  slowly  gyrating.  What 
mysterious  force  sustains  the  wiieel  when  its  only  point  of 
support  is  at  the  end  of  the  axle,  six  or  eight  inches 
away  ?  Scientific  and  popular  literature  were  flooded 
with  explanations  of  this  seeming  paradox.  And  yet  it 
was  nothing  new.  The  boy's  top,  that  spins  and  leans 
and  will  not  fall,  although  solicited  by  gravity,  so  long 
as  it  spins,  which  we  have  seen  all  our  lives  without  spe- 
cial wonder,  is  precisely  the  same  thing. 

Now,  evolution  is  no  new  thing,  but  an  old  familiar 
truth  ;  but,  coming  now  in  a  new  and  questionable  shape, 
lo,  how  it  startles  us  out  of  our  propriety  !  Origin  of 
forms  by  evolution  is  going  on  everywhere  about  us,  both 
in  the  inorganic  and  the  organic  world.  In  its  more  fa- 
niiliar  forms,  it  had  never  occurred  to  most  of  us  that  it 
was  a  scientific  refutation  of  the  existence  of  God,  that  it 
was  a  demonstration  of  materialism.  But  now  it  is  pushed 
one  step  farther  in  the  direction  it  has  always  been  going 
— it  is  made  to  include  also  the  origin  of  species — only  a 
little  change  in  its  form,  and  lo,  how  we  start !  To  the 
deep  thinker,  now  and  always,  there  is  and  has  been  the 
alternative — materialism  or  theism.  God  operates  Nature 
or  Nature  operates  itself ;  but  evolution  puts  no  new 
phase  on  this  old  question.  For  example,  the  origin 
of  the  individual  by  evolution.  Everybody  knows  that 
every  one  of  us  individually  became  what  we  now  are  by 
a  slow  process  of  evolution  from  a  microscopic  spherule 
of  protoplasm,  and  yet  this  did  not  interfere  with  the 

idea  of  God  as  our  individual  maker.    Why,  then,  should 
13  ~"  """^     "^ 


272       EVOLUTION"  AND  EELIGIOUS   THOUGHT. 

the  discovery  that  the  species  (or  first  individuals  of  each 
kind)  originated  by  evolution  destroy  our  belief  in  God 
as  the  creator  of  s^oecies  ? 

3.  It  is  curious  and  very  interesting  to  observe  the 
manner  in  which  vexed  questions  are  always  finally  set- 
tled, if  settled  at  all.  All  vexed  questions — i.  e.,  ques- 
tions which  have  tasked  the  powers  of  the  greatest  minds 
age  after  age — are  such  only  because  there  is  a  real  truth 
on  both  sides.  Pure,  unmixed  error  does  not  live  to 
plague  us  long.  Error,  w^hen  it  continues  to  live,  does 
so  by  virtue  of  a  germ  of  truth  contained.  Great  ques- 
tions, therefore,  continue  to  be  argued  pro  and  con  from 
age  to  age,  because  each  side  is  in  a  sense — i.  e.,  from  its 
own  point  of  view — true,  but  wrong  in  excluding  the 
other  point  of  view  ;  and  a  true  solution,  a  true  rational 
philosophy,  will  always  be  found  in  a  view  which  com- 
bines and  reconciles  the  two  partial,  mutually  excluding 
views,  showing  in  w^hat  they  are  true  and  in  what  they  are 
false — explaining  their  differences  by  transcending  them. 
This  is  so  universal  and  far-reaching  a  principle  that  I 
am  sure  I  will  be  pardoned  for  illustrating  it  in  the 
homeliest  and  tritest  fashion.  I  will  do  so  by  means 
of  the  shield  with  the  diverse  sides,  giving  the  story 
and  construing  it,  however,  in  my  own  way.  There  is, 
apparently,  no  limit  to.  the  amount  of  rich  marrow  of 
truth  that  may  be  extracted  from  these  dry  bones  of 
popular  proverbs  and  fables  by  patient  turning  and 
gnawing. 

We  all  remember,  then,  the  famous  dispute  concern- 


RELATION   OF  EVOLUTION  TO  MATERIALISM.  273 

ing  the  shield,  with  its  sides  of  different  colors,  which 
we  shall  here  call  white  and  black.  We  all  remember 
how,  after  vain  attempts  to  discover  the  truth  by  dis- 
pute, it  was  agreed  to  try  the  scientific  method  of  investi- 
gation. \Ye  all  remember  the  surprising  result.  Both 
parties  to  the  dispute  were  right  and  both  were  wrong. 
Each  was  right  from  his  point  of  view,  but  wrong  in 
excluding  the  other  point  of  view.  Each  was  right  in 
what  he  asserted,  and  each  wrong  in  what  he  denied. 
And  the  complete  truth  was  the  combination  of  the 
partial  truths  and  the  elimination  of  the  partial  errors. 
But  we  must  not  make  the  mistake  of  supposing  that 
truth  consists  in  compromise.  There  is  an  old  adage 
that  truth  lies  in  the  middle  between  antagonistic  ex- 
tremes. But  it  seems  to  us  that  this  is  the  place  of 
safety,  not  of  truth.  This  is  the  favorite  adage,  there- 
fore, of  the  timid  man,  the  time-server,  the  fence-man, 
not  the  truth-seeker.  Suppose  there  had  been  on  the 
occasion  mentioned  above  one  of  these  fence-philoso- 
phers. He  would  have  said  :  ''  These  disputants  are 
equally  intelligent  and  equally  valiant.  One  side  says 
the  shield  is  white,  the  other  that  it  is  black,  now  truth 
lies  in  the  middle  ;  therefore,  I  conclude  the  shield  is 
gray  or  neutral  tint,  or  a  sort  of  ]oepper-and-salt."  Do 
we  not  see  that  he  is  the  only  man  who  has  no  truth  in 
him  ?  No  ;  truth  is  no  heterogeneous  mixture  of  opjio- 
site  extremes,  but  a  stereoscopic  combination  of  two  sur-^ 
face  views  into  one  solid  reality. 

Now,  the  same  is  true  of  all  vexed  questions,  and  I 


274       EVOLUTION   AND  EELIGIOUS  THOUGHT. 

have  given  this  trite  fable  again  only  to  apjjly  it  to  the 
case  in  hand. 

There  are  three  possible  views  concerning  the  origin 
of  organic  forms  whether  individual  or  S23ecific.  Two  of 
these  are  opposite  and  mutually  excluding  ;  the  third 
combining  and  reconciling.  For  example,  take  the  in- 
dividual. There  are  three  theories  concerning  the  ori- 
gin of  the  individual.  The  first  is  that  of  the  pious 
child  who  thinks  that  he  was  made  verv  much  as  he 
himself  makes  his  dirt-nies  :  the  second  is  that  of  the 
street-gamin,  or  of  TojDsy,  -who  sa3^s  :  *^I  was  not  made 
at  all,  I  growed";  the  third  is  that  of  most  intelligent 
Christians— i.  e.,  that  we  were  made  by  a  process  of  evo- 
lution. Observe  that  this  latter  combines  and  reconciles 
the  other  two,  and  is  thus  the  more  rational  and  philo- 
sophical. Now,  there  are  also  three  exactly  correspond- 
ing theories  concerning  the  origin  of  species.  The  first  is 
that  of  many  pious  persons  and  many  intelligent  clerg}'- 
men,  who  say  that  species  were  made  at  once  by  the  Di- 
vine hand  wifJiout  natural  ^^rocess.  The  second  is  that 
of  the  materialists,  who  say  that  species  were  not  made  at 
all,  they  were  derived,  ^^they  growed.''  The  third  is  that 
of  the  theistic  evolutionists,  who  think  that  they  were 
created  by  a  process  of  evolution — who  believe  that  mak- 
ing is  not  inconsistent  with  growing.  The  one  asserts 
the  divine  agency,  but  denies  natural  process;  the  second 
asserts  the  natural  process,  but  denies  divine  agency ;  the 
third  asserts  divine  agency  hy  natural  process.  Of  the 
first  two,  observe,  both  are  right  and  both  wrong ;  each 


RELATION   OF  EVOLUTION  TO   MATERIALISM.  275 

view  is  right  in  what  it  asserts,  and  wrong  in  what  it 
denies — each  is  right  from  its  own  point  of  view,  but 
wrong  in  excluding  the  other  point  of  view.  The  third 
is  the  only  true  rational  solution,  for  it  includes,  com- 
bines, and  reconciles  the  other  two  ;  showing  wherein 
each  is  right  and  wherein  wrong.  It  is  the  combination 
of  the  two  partial  truths,  and  the  elimination  of  the  par- 
tial errors.  But  let  us  not  fail  to  do  perfect  justice. 
The  first  two  views  of  origin,  whether  of  the  individual 
or  of  the  species,  are  indeed  both  partly  wrong  as  well  as 
partly  right ;  but  the  view  of  the  pious  child  and  of  the 
Christian  contains  by  far  the  more  essential  truth.  Of 
the  two  sides  of  the  shield,  theirs  is  at  least  the  whiter 
and  more  beautiful. 

But,  alas !  the  great  bar  to  a  speedy  settlement  of 
this  question  and  the  adoption  of  a  rational  philosophy 
is  not  in  the  head  but  in  the  heart — is  not  in  the  reason 
but  in  pride  of  opinion,  self-conceit,  dogmatism.  The 
rarest  of  all  gifts  is  a  truly  tolerant,  rational  spirit.  In 
all  our  gettings  let  us  strive  to  get  this,  for  it  alone  is 
true  wisdom.  But  we  must  not  imagine  that  all  the 
dogmatism  is  on  one  side,  and  that  the  theological. 
Many  seem  to  think  that  theology  has  a  ^'pre-emptive 
riglit^^  to  dogmatism.  If  so,  then  modern  materialistic 
science  has  ' 'jumped  the  claim.'''  Dogmatism  has  its 
roots  deep-bedded  in  the  human  heart.  It  showed  itself 
first  in  the  domain  of  theology,  because  there  was  the 
seat  of  power.  In  modern  times  it  has  gone  over  to  the 
side  of  science,  because  here  now  is  the  place  of  power 


276       EVOLUTION  AND   RELIGIOUS   THOUGPIT. 

and  fashion.  There  are  tivo  dogmatisms,  both  equally 
opposed  to  the  true  rational  sj^irit,  yiz.,  the  old  theologi- 
cal and  the  new  scientific.  The  old  clings  fondly  to 
old  things,  only  because  they  are  old  ;  the  new  grasps 
eagerly  after  new  things,  only  because  they  are  new. 
True  wisdom  and  true  philosophy,  on  the  contrary,  tries 
all  things  both  old  and  new,  and  holds  fast  only  to  that 
wdiich  is  good  and  true.  The  new  dogmatism  taunts  the 
old  for  credulity  and  superstition  ;  the  old  reproaches 
the  new  for  levity  and  skepticism.  But  true  wisdom 
perceives  that  they  are  both  equally  credulous  and  equal- 
ly skeptical.  The  old  is  credulous  of  old  ideas  and 
skeptical  of  new ;  the  new  is  skeptical  of  old  ideas  and 
credulous  of  new.  Both  deserve  the  unsj)aring  rebuke 
of  all  right-minded  men.  The  appropriate  rebuke  for 
the  old  dogmatism  has  been  already  put  in  the  mouth 
of  Job  in  the  form  of  a  bitter  sneer  :  ^^Xo  doubt  ye  are 
the  people,  and  wisdom  shall  die  with  you.*'  Tiie  ap- 
propriate rebuke  for  the  new  dogmatism,  though  not  put 
into  the  mouth  of  any  ancient  prophet,  ought  to  be  ut- 
tered— I  will  undertake  to  utter  it  here.  I  would  say  to 
these  modern  materialists,  "No  doubt  3^e  are  the  men, 
and  wisdom  and  true  i^hilosophy  were  hor^i  with  you." 

Let  it  be  observed  that  we  are  not  here  touching  the 
general  question  of  the  personal  agency  of  God  in  operat- 
ing JSTature.  This  we  shall  take  up  hereafter.  All  that 
we  wish  to  insist  on  now  is  that  the  process  and  the  law 
of  evolution^does  not  differ  in  its  relation  to  materialism 
from  all  other  processes  and  laws  of  Nature.     If  the 


PvELATIOIT  OF  EVOLUTION   TO   MATERIALISM.  277 

sustentation  of  the  universe  by  the  law  of  gravitation 
does  not  disturb  our  belief  in  God  as  the  sustainer  of 
the  universe,  there  is  no  reason  why  the  origin  of  the 
universe  by  the  law  of  evolution  should  disturb  our 
faith  in  God  as  the  creator  of  the  universe.  If  the  law 
of  gravitation  be  regarded  as  the  Divine  mode  of  susten- 
tation, there  is  no  reason  why  we  should  not  regard  the 
law  of  evolution  as  the  Divine  process  of  creation.  It  is 
evident  that  if  evolution  be  materialism,  then  is  grav^-^ 
itation  also  materialism ;  then  is  every  law  of  Nature 
and  all  science  materialism.  If  there  be  any  difference 
at  all,  it  consists  only  in  this  :  that,  as  already  said,  here 
is  the  last  line  of  defense  of  the  supporters  of  supernatu- 
ralism  in  the  realm  of  Nature.  But  being  the  last  line 
of  defense — the  last  ditch — it  is  evident  that  a  yielding 
here  implies  not  a  mere  shifting  of  line,  but  a  change 
of  base  ;  not  a  readjustment  of  details  only,  but  a  recon- 
struciio7i  of  Christian  theology.  This,  I  believe,  is  in- 
deed necessary.  There  can  be  little  doubt  in  the  mind 
of  the  thoughtful  observer  that  we  are  even  now  on  the 
eve  of  the  greatest  change  in  traditional  views  that  has 
taken  place  since  the  birth  of  Christianity.  But  let  no 
one  be  greatly  disturbed  thereby.  For  as  then,  so  now, 
change  comes  not  to  destroy  but  to  fulfill  all  our  dearest 
hopes  and  aspirations ;  as  then,  so  now,  the  germ  of 
living  truth  has,  in  the  course  of  ages,  become  so  en- 
crusted with  meaningless  traditions  wliich  stifle  its 
growth,  that  it  is  necessary  to  break  the  shell  to  set  it 
free ;  as  then,  so  now,  it  has  become  necessary  to  purge 


278       EVOLUTION   AND   EELIGIOUS   THOUGHT. 

religious  belief  of  dross  in  the  form  of  trivialities  and 
superstitions.  This  has  ever  been  and  ever  will  be  the 
function  of  science.  The  essentials  of  religious  faith  it 
does  not,  it  can  not,  touch,  but  it  purifies  and  ennobles 
our  conceptions  of  Deity,  and  thus  elevates  the  whole 
plane  of  religious  thought. 

It  will  not,  of  course,  be  expected  of  me  to  give,  even 
in  briefest  outline,  a  svstem  of  reconstructed  Christian 
thought.  Such  an  attempt  would  be  wholly  unbecoming. 
Time,  very  much  time,  and  the  co-operation  of  many 
minds,  bringing  contributions  from  many  departments 
of  thought,  is  necessary  for  this.  In  a  word,  it  can  only 
itself  come  by  a  gradual  process  of  evolution.  But  from 
the  point  of  view  of  science  some  very  fundamental 
changes  in  traditional  views  are  already  plain.  Of  these 
the  most  fundamental  and  important  are  our  ideas  con- 
cerning God,  Nature,  and  man  in  their  relations  to  one 
another.  These  will  form  the  subject  of  the  next  three 
cliapters. 


/  OHAPTEr"  III. 


/ 


THE   RELATIONS'   OF   GOD   TO   I^ATURE. 

rWE  have  already  said  that  evolution  does  not  differ 
essentially  from  other  laws  of  ]N"ature  in  its  hearing  on 
^  religious  helief.  It  only  reiterates  and  enforces  with 
additional  emphasis  what  Science,  in  all  its  departments, 
has  heen  saying  all  along.  The  difficulties  in  the  way  of 
certain  traditional  views  have  pressed  with  ever  increas- 
ing force  upon  the  thoughtful  mind  ever  since  the  birth 
of  modern  science.  All  along,  an  issue  has  been  gather- 
ing, but  put  off  from  time  to  time  by  compromise,  until 
now,  at  last,  the  issue  is  forced  upon  us  and  compromise 
is  exhausted.  The  issue  (let  us  look  it  squarely  in  the 
face)  is  :  Either  God  is  far  more  closely  related  with  Na- 
ture, and  operates  it  in  a  more  direct  way  than  we  have 
recently  been  accustomed  to  think,  or  else  (mark  the  al- 
ternative) Nature  operates  itself  and  needs  no  God  at 
all.     There  is  no  middle  ground  tenable. 

Let  us  trace  rapidly  the  growth  of  this  issue.  The 
old  idea>and  the  most  natural  to  the  religious  mind  was 
the  direct  agency  of  God  in  every  event  and  phenomenon 
of  Nature.     This  view  is  nobly  expressed  in  the  noblest 


280       EVOLUTION  AND  EELIGIOUS  THOUGHT. 

literature  in  the  world — in  the  Hebrew  and  Christian 
Scriptures  :  ^'He  looketh  on  the  earth  and  it  trembleth. 
He  toucheth  the  hills  and  they  smoke."  *'He  maketh 
his  sun  to  rise  on  the  evil  and  on  the  good,  and  sendeth 
his  rain  on  the  just  and  on  the  unjust."  But  now  comes 
Science  and  exj^lains  all  these  phenomena  by  natural  laws 
and  resident  forces,  and  we  all  accept  her  explanation. 
Thus,  one  by  one  the  2ihenomena  of  Xature  are  explained 
by  the  operation  of  resident  forces  according  to  natural 
laws,  until  the  whole  course  of  Kature,  as  we  now  know 
it,  has  been,  or  will  be,  or  conceivably  may  be,  thus  ex- 
j)lained. 

Thus  has  gradually  grown  up,  without  our  confessing 
it,  a  kind  of  scientific  polytheism — one  great  Jehovah, 
perhaps,  but  with  many  agents  or  sub-gods,  each  inde- 
pendent, efficient,  and  doing  all  the  real  work  in  his  own 
domain.  The  names  of  these,  our  gods,  are  gravity,  light, 
heat,  electricity,  magnetism,  chemical  affinity,  etc.,  and 
we  are  practically  saying :  "  These  be  your  gods,  0 
Israel,  which  brought  you  out  of  the  land  of  Egyptian 
darkness  and  ignorance.  These  be  the  only  gods  ye 
need  fear,  and  serve,  and  studv  the  wavs  of." 

What,  then,  is  practically  the  notion  which  most 
people  seem  to  have  of  the  relation  of  Deity  to  Nature  ? 
It  is  that  of  a  great  master-mechanic  far  away  above  us 
and  beyond  our  reach,  who  once  upon  a  time,  long  ago, 
and  once  for  all,  worked,  created  matter,  endowed  it  with 
necessary  properties  and  powers,  constructed  at  once  out 
of    hand   this   wonderful    cosmos   with    its    numberless 


THE  RELATION   OF  GOD   TO   NATUPwE.         281 

wheels  within  wheels,  endowed  it  with  forces,  put  springs 
in  it,  wound  it  up,  set  it  a-going,  and  then — rested. 
The  thing  has  continued  to  go  of  itself  ever  since.  He 
might  have  not  only  rested  but  slept,  and  the  thing: 
would  have  gone  of   itself.     He   might  not   only   have 


slept  but  diecL  {in(;|  still  the  thing  would  have  continued 
to  go  of  itself.  ^  But,  no,  I  forget.  He  must  not  sleep  or 
die,  for  the  work  is  not  absolutely  perfect.  There  are 
some  things  too  hard  even  for  Him  to  do  in  this  master- 
ful, god-like  way.  There  are  some  things  which  even  He 
can  not  do  except  in  a  'prentice-like,  man-like  way.  The 
hand  must  be  introduced  from  time  to  time  to  repair,  to 
rectify,  to  improve,  especially  to  introduce  new  parts, 
such  as  new  organic  forms. 

Such  was  the  state  of  the  compromise  until  twenty- 
five  years  ago.  J^ature  is  sufficient  of  itself  for  its  course 
and  continuance,  but  not  for  origins  of  at  least  some  new 
parts.  Such  was  the  state  of  the  compromise  until  Dar- 
win and  the  theory  of  evolution.  But,  now,  even  this 
poor  privilege  of  occasional  interference  is  taken  away. 
Now,  origins,  as  well  as  courses,  are  reduced  to  resident 
forces  and  natural  law.     Now,  Nature  is  sufficient  of  it- 

^  self,  not  only  for  sustentation,  but  also  for  creation. 
Thus,  Science  has  seemed  to  push  Him  farther  and  far- 

/  ther  away  from  us,  until  now,  at  last,  if  this  view  be 
true,  evolution  finishes  the  matter  by  pushing  Him  en- 
tirely out  of  the  universe  and  dispensing  with  Him  alto- 
gether. Th2S,_of  course,  is  materialism.  But  this  is  no 
new  view  now  brought  forward  for  the  first  time  by  evo- 


282      EVOLUTION   AND  EELIGIOUS  THOUGHT. 

lution.  On  the  contrary,  evolution  only  finishes  what 
science  has  been  doing*  all  along. 

See,  then,  how  the  issue  is  forced.  Either  Kature  is 
sufficient  of  itself  and  wants  no  God  at  all,  or  else  this 
whole  idea,  the  history  of  which  we  have  been  tracing,  is 
radically  false.  "We  have  here  given  by  science  either  a 
demonstration  of  materialism  or  else  a  reductio  ad  ab- 
surdum.  Which  is  it  ?  I  do  not  hesitate  a  moment  to 
say  it  is  a  reductio  ad  absurdum.  And  I  believe  that 
evolution  has  conferred  an  inestimable  benefit  on  phi- 
losophy and  on  religion  by  forcing  this  issue  and  com- 
pelling us  to  take  a  more  rational  view. 

What,  then,  is  the  alternative  view  ?  It  is  the  utter 
rejection  with  Berkeley  and  with  Swedenborg  of  the  in- 
dependent existence  of  matter  and  the  real  efficient 
agency  of  natural  forces.  It  is  the  frank  return  to  the 
old  idea  of  direct  divine  agency,  but  in  a  new,  more  ra- 
tional, less  anthropomorphic  form.  It  is  the  bringing 
together  and  complete  reconciliation  of  the  two  appar- 
ently antagonistic  and  mutually  excluding  views  of  di- 
rect agency  and  naturcd  laiv.  Such  reconciliation  we 
have  already  seen  is  the  true  test  of  a  rational  philosophy. 
It  is  the  belief  in  a  God  not  far  away  beyond  our  reach, 
who  once  long  ago  enacted  laws  and  created  forces  which 
continue  of  themselves  to  run  the  machine  we  call  Na- 
ture, but  a  God  immanent,  a  God  resident  m  Nature, 
at  all  times  and  in  all  places  directing  every  event  and 
determining  every  phenomena — a  God  in  whom  in  the 
most  literal  sense  not  only  we  but  all  things  have  their 


TOE   RELATIO:^'  OF  GOD   TO   NATURE.         283 

being,  in  whom  all  things  consist,  through  whom  all 
things  exist,  and  without  whom  there  would  be  and  could 
be  nothing.  According  to  this  view  the  phenomena  of 
Nature  are  naught  else  than  objectified  modes  of  divine 
thought,  the  forces  of  Nature  naught  else  than  different 
forms  of  one  omnipresent  divine  energy  or  will,  the 
laws  of  Nature  naught  else  than  the  regular  modes  of 
operation  of  that  divine  w^ill,  invariable  because  He  is 
unchangeable.  According  to  this  view  the  law  of  gravi- 
tation is  naught  else  than  the  mode  of  operation  of  the 
divine  energy  in  sustaining  the  cosmos — the  divine  meth- 
od of  sustentation  ;  the  law  of  evolution  naught  else 
than  the  mode  of  operation  of  the  same  divine  energy 
in  originating  and  developing  the  cosmos — the  divine 
method  of  creation  ;  and  Science  is  the  systematic  knowl- 
edge of  these  divine  thoughts  and  ways — a  rational  sys- 
tem of  natural  theology.  In  a  word,  according  to  this 
view,  there  is  no  real  efficient  force  but  spirit,  and  no 
real  independent  existence  but  God. 

But  some  will  object  that  this  is  pure  Idealism.  Yes, 
but  far  different  from  what  usually  goes  under  that 
name.  The  ideal  philosophy  as  usually  understood  re- 
gards the  external  world  as  having  no  real  objective  ex- 
istence outside  of  ourselves — as  objectified  mental  states 
of  the  observer — as  literally  such  stuff  as  dreams  are  made 
of — as  a  mere  phantasmagoria  of  trooping  shadows  bav- 
in sr  no  real  existence  but  in  the  mind  of  the  dreamer, 
and  each  dreamer  makes  his  own  world.  Not  so  in  the 
idealism  above  presented.     According  to  tMs  the  exter- 


284       EVOLUTION   AND   RELIGIOUS   THOUGHT. 

nal  world  is  the  objectified  niodeSj  not  of  tlie  mind  of 
the  observer,  but  of  the  mind  of  God.  According  to 
this,  the  external  world  is  not  a  mere  unsubstantial  fig- 
ment or  dream,  but  for  us  a  very  substantial  objective 
reality  surrounding  us  and  conditioning  us  on  every 
side. 

Again,  it  will  be  objected  that  this  is  pure  Pantheism. 
Again,  we  answer  ^'yes."  Call  it  so  if  you  like,  but  far 
different  from  what  goes  under  that  name,  far  different 
from  the  pantheism  which  sublimates  the  personality  of 
the  Deity  into  all-pervading  unconscious  force,  and 
thereby  dissipates  all  our  hopes  of  personal  relation  with 
him.  Properly  understood,  we  believe  this  view  com- 
pletely reconciles  the  two  antagonistic  and  mutually  ex- 
cluding views  of  impersonal  pantheism  and  anthropomor- 
phic personalism,  and  is  therefore  more  rational  than 
either.  The  discussion  of  this  most  important  point  can 
only  come  up  after  the  next  chapter,  because  the  argu- 
ment for  the  personality  of  Deity  is  derived,  not  from 
without  by  the  study  of  Nature,  but  from  within  in  our 
own  consciousness.  We  therefore  put  off  its  discussion 
for  the  present. 

But,  finally,  some  will  object,  *'We  can  not  live  and 
work  effectively  under  such  a  theory  unless,  indeed,  we 
escape  through  pantheism."  It  may,  alas  !  be  true  that 
this  view  brings  us  too  near  Him  in  our  sense  of  spiritual 
nakedness  and  shortcoming.  It  may,  indeed,  be  that  we 
can  not  live  and  work  in  the  continual  realized  presence 
of  the  Infinite.     It  may,  indeed,  be  that  we  must  still 


TUE   RELATION   OF   GOD   TO  NATURE.         285 

wear  the  veil  of  a  practical  materialism  on  our  hearts  and 
minds.  It  may,  indeed,  be  that  in  our  practical  life  and 
scientific  work  we  must  still  continue  to  think  of  natural 
forces  as  efficient  agents.  But,  if  so,  let  us  at  least  re- 
member that  this  attitude  of  mind  must  be  regarded  only 
as  our  ordinary  work-clothes — necessary  work-clothes  it 
may  be  of  our  outer  lower  life — to  be  put  aside  when  we 
return  home  to  our  inner  higher  life,  religious  and  philo- 
sophical. 


CHAPTER  IV. 

THE   KELATIO^^   OF   MAX   TO   MATURE. 

There  are  two  widely  distinct  views  concerning  the 
relation  of  man  to  Nature  ;  the  one  as  old  as  the  history 
of  human  thought,  the  other  only  now  urged  upon  us 
by  modern  science.  According  to  the  one,  man  is  the 
counterpart  and  equivalent  of  Xature.  He  alone  has — 
in  fact  is — an  immortal  spirit,  and  therefore  he  belongs 
to  a  world  of  his  own.  According  to  the  other,  man  is 
but  a  part,  a  very  insignificant  part  of  Nature,  and  con- 
nected in  the  closest  way  with  all  other  parts,  especially 
with  the  animal  kingdom.  He  has  no  world  of  his  own, 
nor  even  kingdom  of  his  own  :  he  belongs  to  the  animal 
kingdom.  In  that  kingdom  he  has  no  deiiartment  of 
his  own  :  he  is  a  vertebrate.  In  the  department  of  verte- 
brates he  has  no  privileged  class  of  his  own  :  he  is  a 
mammal.  In  the  class  of  mammals  he  has  no  titled 
order  of  his  own  :  he  is  a  primate,  and  shares  his  pri- 
macy with  apes.  It  is  doubtful  if  he  may  enjoy  the  pri- 
vacy of  a  family  of  his  own — the  Hominidae — for  the 
structural  differences  between  man  and  the  anthropoid 
apes  are  probably  not  so  great  as  between  the  sheep 
family  and  the  deer  family. 


THE  RELATION   OF  MAN   TO   NATURE.        2S7 

i^ow  it  is  evident  that  these  two  are  only  views  from 
different  points,  psychical  and  structural.  From  the 
psychical  point  of  view  it  is  simply  impossible  to  exag- 
gerate the  wideness  of  the  gap  that  separates  man  from 
even  the  highest  animals.  From  this  point  of  view 
man  must  be  set  over  as  an  equivalent,  not  only  to  the 
whole  animal  kingdom,  but  to  the  whole  of  Nature  be- 
sides. From  the  structural  point  of  view,  on  the  con- 
trary, it  is  impossible  to  exaggerate  the  closeness  of  the 
connection.  Man's  body  is  identified  with  all  Nature  in 
its  chemical  constituents,  with  the  body  of  all  animals 
in  its  functions,  with  all  vertebrates,  especially  mammals, 
in  its  structure.  Bone  for  bone,  muscle  for  muscle, 
ganglion  for  ganglion,  almost  nerve-fiber  for  nerve-fiber, 
his  body  corresponds  with  that  of  the  higher  animals. 
Whether  he  was  derived  from  lower  animals  or  not,  cer- 
tain it  is  that  his  structure  even  in  the  minutest  details 
is  precisely  such  as  it  would  be  if  he  were  thus  derived 
by  successive  slight  modifications. 

Now,  of  these  two  views,  the  latter  has  been  in  recent 
times  enormously  productive  in  increasing  our  knowl- 
edge. Anatomy  has  become  truly  scientific  only  through 
comparative  anatomy  ;  physiology  through  comparative 
physiology  ;  embryology  through  comparative  embryol- 
ogy. Sociology  is  fast  following  in  the  same  line,  and 
becoming  scientific  through  comparative  sociology.  Is 
not  the  same  true  also  of  psychology  ?  Will  not  psy- 
chology become  truly  scientific  only  through  comparative 
psychology,  i.  e.,  by  the  study  of  the  spirit  of  man  in  re- 


288       EVOLUTION  AND  RELIGIOUS  THOUGHT. 

lation  to  what  corresponds  to  it  in  lower  animals  ?  But 
this  yiew  and  this  method,  when  pushed  to  what  seems 
to  many  their  logical  conclusion,  end  in  identification  of 
man  with  mere  animals,  of  spirit  with  mere  physical  and 
chemical  forces,  immortality  with  mere  conservation  of 
energy,  and  thus  leads  to  blank  and  universal  materialism. 
Thus,  while  it  increases  our  knowledge,  it  destroys  our 
hopes.  Is  there  any  escape  ?  There  is.  The  two  extreme 
views  given  above  are  not  irreconcilable.  As  already 
said,  they  are  only  views  from  different  points,  and  there- 
fore, although  both  true,  are  equally  one-sided  and  partial, 
and  a  true  and  rational  philosophy,  in  this  as  in  all  other 
cases  of  vexed  questions,  is  found  only  in  a  liigher  view, 
which  combines  and  reconciles  these  mutually  excluding 
extremes.     Can  we  find  such  a  view  ?     I  think  we  can. 

Let  us  first,  however,  trace  some  of  the  stages  of  this 
scientific  materialism.  There  are  two  main  branches 
of  the  argument  for  materialism  :  one  derived  from 
hrain-physiology,  the  other  from  evolution.  As  we  wish 
to  be  perfectly  fair,  w^e  will  present  and  even  joress  the 
argument  in  both  these  directions,  although  the  latter 
alone  bears  directly  on  the  subject  in  hand. 

In  recent  times,  physiology  has  made  great  and,  to 
many,  startling  advances  in  the  direction  of  connecting 
mental  phenomena  with  brain-changes.  Physiologists 
have  established  the  correlation  of  vital  with  chemical 
and  ph3^sical  forces,*  and   probably   in   some   sense,  at 


* 


See  an  article  by  the  author  on  this  subject,  "  American  Journal  of 


THE  RELATION  OF  MAN  TO  NATURE. 

least,  of  mental  with  yital  forces.  They  have  proVe^ia 
every  act  of  perception,  first  a  physical  change  in  a  nerve- 
terminal,  then  a  propagated  thrill  along  a  nerve-fiber, 
and  then  a  resulting  change,  physical  or  chemical,  in  the 
brain  ;  and  in  every  act  of  volition,  a  change  first  in  a 
brain-cell,  then  a  return  thrill  along  a  nerve-fiber,  and  a 
resulting  contraction  of  a  muscle.  Even  the  velocity  of 
the  transmission  to  and  fro  has  been  measured,  and 
the  time  necessary  to  produce  brain-changes  estimated. 
They  have  also  established  the  existence  of  physical  and 
chemical  changes  in  the  brain  corresponding  to  every 
change  of  mental  state,  and  with  great  probability  an 
exact  quantitative  relation  between  these  changes  of 
brain  and  the  corresponding  changes  of  mind.  In  the 
near  future  they  may  do  more  :  they  may  localize  all  the 
different  faculties  and  powers  of  the  mind,  each  in  its 
several  place  in  the  brain,  and  thus  lay  the  foundations 
of  a  truly  scientific  phrenology.  In  the  far-distant  fu- 
ture we  may  possibly  do  much  more.  We  may  connect 
each  kind  of  mental  state  wnth  a  different  and  distinctive 
kind  of  brain-change.  We  may  find,  for  example,  a 
right-handed  rotation  of  atoms  associated  with  love,  and 
a  left-handed  rotation  associated  with  hate,  or  a  gentle 
sideways  oscillation  associated  with  consciousness,  and  a 
vertical  pounding  associated  with  ivill.  Now,  suj^pose 
all  this,  and  even  much  more,  be  done  in  the  way  of 
associating,  both  in  degree  and  in  kind,  mental  changes 


Science,"  series  ii,  vol.  xxviii,  p.  305,  1859,  and  in  ''Popular  Science 
Monthly,"  vol.  iv,  p.  156,  1873. 


290      EVOLUTION  AND  RELIGIOUS  THOUGHT. 

with  brain-clianges.  What  then  ?  '^  Why,"  say  the  ma- 
terialists, "we  thereby  identify  mzVic?  with  matter,  men- 
tal forces  with  material  forces.  Thought,  emotion,  con- 
sciousness and  will  become  products  of  the  brain,  in  the 
same  sense  as  bile  is  a  product  of  the  liver,  or  urea  a 
product  of  the  kidneys." 

Such  is,  in  brief,  the  argument.  !N'ow,  the  answer  : 
We  may  do  all  we  have  supposed  and  much  more.  AVe 
may  push  our  knowledge  in  this  direction  as  far  as  the 
boldest  imagination  can  reach,  and  even  then  we  are  no 
nearer  the  solution  of  this  mystery  of  the  relation  of 
brain-changes  and  mental  changes  than  we  are  now. 
Even  then  it  would  be  impossible  for  us  to  conceive  how 
brain-changes  produce  mental  changes  or  vice  versa. 
Physical  changes  in  sense-organs,  transmitted  along 
nerve-fibers,  determine  changes  in  brain-substance.  So 
much  is  intelligible.  But  now  there  appear — how  it  is 
impossible  to  imagine — consciousness,  thought,  emotion, 
etc. — phenomena  of  an  entirely  different  order,  belong- 
ing to  an  entirely  different  world.  So  different,  that  it  is 
impossible  to  imagine  the  nature  of  the  nexus  between, 
or  to  construe  the  one  in  terms  of  the  other.  Brain-cells 
are  agitated  and  thought  appears  :  Aladdin's  lamp  is 
rubbed,  and  the  genie  appears.  There  is  just  as  much 
intelligible  causal  relation  between  the  two  sets  of  phe- 
nomena in  the  one  case  as  in  the  other. 

Now,  this  mystery  is  not  of  the  nature  of  those  which 
disappear  under  the  light  of  knowledge.  On  the  con- 
trary, science  only  brings  it  out  in  sharper  relief,  and 


THE  KELATION  OF  MAN  TO  NATUEE.   291 

emphasizes  its  absolute  unsolvableness.  Suppose  an  ab- 
solutely perfect  knowledge,  i^erfect  in  degree,  but  human 
in  kind.  Suppose  an  ideally  perfect  science — a  science 
which  has  so  completely  subdued  its  domain,  and  re- 
duced it  to  such  perfect  simplicity,  that  the  whole  cos- 
mos may  be  expressed  in  a  single  mathematical  formula 
— a  formula  which,  worked  out  with  plus  signs,  would 
give  every  phenomenon  and  event  which  shall  ever  occur 
in  the  future,  and  with  minus  signs  every  phenomenon 
and  event  which  has  ever  occurred  in  the  past.  Surely, 
this  is  an  ideally  perfect  science.  Yet,  even  to  such  a 
science,  the  relation  of  brain-changes  to  mental  states 
would  be  as  great  a  mystery  as  now.  It  would  even 
come  out  in  stronger  relief,  because  so  many  other  ap- 
parent mysteries  would  disappear.  Like  the  essential 
nature  of  matter  or  the  ultimate  cause  of  force,  this  rela- 
tion lies  evidently  beyond  the  domain  of  science.  It  re- 
quires some  other  hind  of  knowledge  than  human  to 
understand  it. 

But  materialists  insist  so  much  on  the  identity  of 
brain-physiology  with  psychology,  that  even  at  the  risk 
of  tediousness  we  will  multiply  illustrations  in  order,  if 
possible,  to  make  this  point  still  clearer.  Suppose,  then, 
we  exposed  the  brain  of  a  living  man  in  a  state  of  intense 
activity.  Suppose,  further,  that  our  senses  were  abso- 
lutely perfect,  so  that  we  could  see  every  change,  of 
whatever  sort,  taking  place  in  the  brain-substance. 
What  would  we  see  ?  Obviously  nothing  but  molecular 
changes,  physical  and  chemical ;  for  to  the  outside  ob- 


292       EVOLUTION   AND  EELIGIOUS  THOUGHT. 

server  there  is  absolutely  nothing  else  there  to  see.  But 
the  subject  sees  nothing  of  all  this.  His  experiences  are 
of  a  different  order,  viz.,  consciousness,  thought,  emo- 
tions, etc.  Viewed'  from  the  outside,  there  is — there  can 
be — nothing  but  motions  ;  viewed  from  the  inside,  noth- 
ing but  thought,  etc. — from  the  one  side,  only  pliysical 
phenomena ;  from  the  other  side,  only  psychical  phe- 
nomena. Is  it  not  plain  that,  from  the  very  nature  of 
the  case,  it  must  ever  be  so  ?  Certain  vibrations  of  brain 
molecules,  certain  oxidations  with  the  formation  of  car- 
bonic acid,  water,  and  urea  on  the  one  side,  and  there 
appear  on  the  other  sensations,  consciousness,  thoughts, 
desires,  volitions.  There  are,  as  it  w^re,  two  sheets  of 
blotting-paj^er  jDasted  together.  The  one  is  the  brain, 
the  other  the  mind.  Certain  ink-scratches  or  blotches, 
utterly  meaningless  on  the  one,  soak  through  and  appear 
on  the  other  as  intelUgihle  writing,  but  how  we  know 
not,  and  can  never  hope  to  guess.  But  wdien  the  paste 
dissolves,  shall  the  writing  remain^    We  shall  see. 

But  some  will  object.  There  is  nothing  specially 
strange  and  unique  in  all  this,  for  the  same  mystery  un- 
derlies the  essential  nature  of  all  kinds  of  force  and 
matter,  and  therefore  all  phenomena.  True  enough, 
but  with  this  difference.  Physical  and  chemical  forces 
and  phenomena  are  indeed  incomprehensible  in  their  es- 
sential nature ;  but  once  accept  their  existence,  and  all 
their  different  forms  are  mutuallv  convertible,  construa- 
ble  In  terms  of  each  other  and  all  in  terms  of  motion. 
But  it  is  impossible  by  any  stretch  of  the  imagination 


THE   RELATION   OF  MAN   TO  NATURE.        293 

to  thus  construe  mental  forces  and  mental  phenomena. 
It  may,  indeed,  be  impossible  to  conceive  lioio  came  the 
plane  of  material  existence,  but,  standing  on  that  plane, 
all  phenomena  fall  into  intelligible  order.  But  there 
is  another  plane  above  this  one,  having  no  intelligible 
relation  with  it.  We  must  climb  up  and  stand  on  this 
before  its  phenomena  fall  into  intelligible  order.  In 
a  word,  material  forces  and  phenomena  are,  indeed,  a 
mystery,  but  only  of  the  p^st  order.  But  mental  and 
moral  forces  and  phenomena  are  a  mystery  even  from  the 
standpoint  of  the  other,  and  are  therefore  a  mystery  of 
the  second  order — a  mystery  withm  a  mystery. 

We  repeat,  then,  with  additional  emphasis  after  this 
examination,  that  we  can  not  imagine  between  physical 
and  psychical  phenomena  a  relation  of  cause  and  effect 
in  the  same  sense  in  which  we  use  these  terms  in  physi- 
cal science,  although  in  some  sense  there  is  doubtless 
such  a  relation.  If  man  were  the  only  animal  we  had 
to  deal  with,  there  would  be  no  standing  ground  left  for 
materialism.  But  there  is  still  another  difficultv  which 
sticks  deeper.  It  is  that  suggested  by  the  laio  of  evolu- 
tion and  enforced  by  the  comparative  method. 

Relation  of  Man  to  Animals. — Man,  we  say,  is  en- 
dowed with,  is,  in  fact,  an  immortal  spirit.  What  is 
spirit  ?  We  know  things  only  by  their  phenomena ; 
what  are  the  phenomena  of  spirit  ?  Consciousness,  will, 
intelligence,  memory,  love,  liate,  fear,  desire  —  surely 
these  are  some  of  them.  But  has  not  a  dog  or  a  monkey 
all  these  ?    Pressed  with  this  difficulty,  some  have  in- 


294       EVOLUTIOI^  AND  KELIGIOUS  THOUGHT. 

deed  felt  compelled  to  accord  immortal  spirit  to  higher 
animals.  But  we  can  not  stop  here.  If  to  these,  then 
also  to  all  animals  ;  for  we  haye  here  only  a  sliding  scale 
without  break.  Can  we  stop  now  and  make  it  coexten- 
sive Avith  sentiency  ?  No  ;  for  the  lowest  animals  and 
lowest  plants  merge  into  each  other  so  completely  that 
no  one  can  draw  the  line  between  them  with  certainty. 
We  must  extend  it  to  plants  also.  Shall  we  stop  here 
and  make  immortal  spirit  coextensive  with  life  ?  We 
can  not ;  for  life-force  is  certainly  correlated  with,  trans- 
mutable  into,  and  derivable  from,  physical  and  chemical 
forces.  AVe  must  extend  it  into  dead  nature  also. 
Therefore,  everything  is  immortal  or  none.  Our  boasted 
immortality  resolves  itself  into  indestructibility  of  mat- 
ter and  force,  but  not  of  form,  nor  of  consciousness  and 
lyersonality.  Such  an  immortality  is  of  no  value  to  us. 
Thus,  then,  if  once  we  pass  the  gap  between  man  and 
the  higher  animals,  there  is  no  possibility  of  a  stopping- 
place  anywhere. 

Such  is  the  difficulty  presented  by  comparison  in  the 
taxonomic  series.  Take  now  the  embryonic  series.  Each 
one  of  us,  individually,  was  formed  gradually  by  a  pro- 
cess of  evolution,  from  a  microscopic  spherule  of  proto- 
plasm undistinguishable  in  structure  from  the  lowest 
forms  of  protozoal  life.  Now,  in  this  gradual  process  of 
evolution,  where  did  immortal  spirit  come  in  ?  Was  it 
in  the  germ-cell  ?  Then  why  deny  it  to  the  i:>rotozoan  ? 
Was  it  at  the  quickening,  or  at  the  birth,  or  at  the  mo- 
ment of  first  self -consciousness,  or  at  some  later  period  of 


THE   EELATION"   OF  MAN   TO   NATURE.        295 

capacity  of  abstract  thought  ?  Again,  when  it  did  come 
in,  was  it  something  superadded  or  did  it  grow  out  of 
something  ah-eady  existing  in  the  embryo  or  the  infant  ? 

Or  take  the  evolution  series  from  protozoan  to  man. 
This  we  have  ah'eady  seen  is  similar  in  outline  to  the 
other  two.  JS'ow,  in  the  gradual  evolution  of  the  animal 
kingdom  throughout  all  geological  time,  terminating  in 
man,  when  did  immortal  spirit  come  in  ?  Did  it  enter 
with  life,  or  with  sentient  life,  or  somewhere  in  the 
ascending  scale  of  animals,  or  with  the  advent  of  man  ? 
If  with  man,  was  it  some  new  thing  added  at  once  out 
of  hand,  or  did  it  grow  out  of  something  already  exist- 
ing in  animals  ? 

This  last,  we  are  persuaded,  is  the  only  tenable  view — 
the  only  view  that  can  effect  that  reconciliation  between 
the  two  extreme,  mutually  excluding  views  now  usually 
held,  which,  as  already  seen,  is  the  true  test  of  a  rational 
philosophy.  I  believe  that  the  spirit  of  man  luas  devel- 
oped out  of  the  anima  or  conscious  principle  of  animals, 
and  that  this,  again,  was  developed  out  of  the  lower  forms 
of  life-force,  and  this  in  its  turn  out  of  the  chemical  and 
physical  forces  of  Nature  ;  and  that  at  a  certain  stage  in 
this  gradual  development,  viz.,  with  man,  it  acquired i\\Q 
property  of  immortality  precisely  as  it  now^,  in  the  indi- 
vidual history  of  each  man  at  a  certain  stage,  acquires 
the  capacity  of  abstract  thought.  This  is,  in  brief,  the 
view  which  I  wish  to  enforce.  The  reader  must  under- 
stand, however,  that  this  is  my  oiun  vieio  only,  a  view  for 
which  I  have  earnestly  contended  for  twenty  years.  It 
14 


296       EVOLUTION   AND  RELIGIOUS   THOUGHT. 

appeals,  therefore,  not  to  authority,  but  only  to  reason. 
I  wish  now  to  present  it  as  briefly  as  possible. 

First,  then,  I  would  draw  attention  to  the  fact  that 
there  is  nothing  wholly  exceptional  in  such  transforma- 
tion with  the  sudden  appearance  of  new  powers  and 
properties  ;  but,  on  the  contrary,  it  is  in  accordance  with 
many  analogies  in  the  lower  forces,  and  therefore  a 
priori  not  only  credible  but  probable.  For  example, 
force  and  matter  may  be  said  to  exist  noiv  on  several 
distinct  planes  raised  one  above  another.  There  is  a  sort 
of  taxonomic  scale  of  force  and  matter.  These  are,  1, 
the  plane  of  elements  ;  2,  the  plane  of  chemical  com- 
pounds ;  3,  the  plane  of  vegetal  life  ;  4,  the  plane  of 
animal  life  ;  and  5,  the  plane  of  rational  and,  as  we  hope, 
immortal  life.  Each  plane  has  its  own  appropriate  force 
and  distinctive  phenomena.  On  the  first  operates  physi- 
cal forces,  producing  physical  phenomena  only  —  for 
the  oi^eration  of  chemical  affinity  immediately  raises  mat- 
ter to  the  next  plane.  On  the  second  plane  operates,  in 
addition  to  physical,  also  chemical  forces,  producing  all 
those  changes  by  action  and  reaction,  the  study  of  which 
constitutes  the  science  of  chemistry.  On  the  third  plane, 
in  addition  to  the  two  preceding  forces,  with  their  char- 
acteristic iihenomena,  operates  also  life-force,  produc- 
ing the  distinctive  phenomena  characteristic  of  living 
things.  On  the  fourth  plane,  in  addition  to  all  lower 
forces  and  their  phenomena,  operates  also  a  higher  form 
of  life-force  characteristic  of  animals,  producing  the  phe- 
nomena characteristic  of  sentient  life,  such  as  sensation. 


THE   RELATION    OF  MAN   TO  NATURE.        297 

consciousness,  and  will.  On  the  fifth  plane,  in  addition 
to  all  the  preceding  forces  and  phenomena,  we  have  also 
the  forces  and  phenomena  characteristic  of  rational  and 
moral  life. 

Now,  although  there  are  doubtless  great  differences  of 
level  on  each  of  these  planes,  yet  there  is  a  very  distinct 
break  between  each.  Although  there  are  various  degrees 
of  the  force  characteristic  of  each,  yet  the  difference  be- 
tween the  characteristic  forces  is  one  of  kind  as  well  as  of 
degree.  Although  energy  by  transmutation  may  take  all 
these  different  forms,  and  thus  does  now  circulate  up  and 
down  through  all  these  planes,  yet  the  passage  from  one 
plane  upward  to  another  is  not  a  gradual  passage  by  slid- 
ing scale,  but  at  one  hound.  When  the  necessary  condi- 
tions are  present,  a  new  and  higher  form  of  force  at  once 
appears,  Wke  a  Mrtli  into  a  higher  sphere.  For  example, 
when  hydrogen  and  oxygen  are  brought  together  under 
proper  conditions,  water  is  born — a  new  thing  with  new 
and  wiiolly  unexpected  properties  and  powers,  entirely 
different  from  those  of  its  components.  When  C0„,  H^O, 
and  NH3  are  brought  together  under  suitable  conditions, 
viz.,  in  the  green  leaves  of  plants,  in  the  presence  of  sun- 
light, living  protoplasm  is  then  and  there  born,  a  some- 
thing having  entirely  new  and  unexpected  powers  and 
properties.  It  is  no  gradual  process  but  sudden,  like  birth 
into  a  higher  sphere. 

Now,  there  is  not  the  least  doubt  that  the  same  is  true 
of  the  order  and  manner  of  the  first  appearance  of  the 
natural  forces  in  the  phylogenic  series.     In  the  history  of 


298       EVOLUTION  AND  RELIGIOUS   THOUGHT. 

the  evolution  of  the  cosmos,  the  forces  of  Nature  have 
appeared  successively  and  suddenly  when  conditions  be- 
came favorable.  There  was  a  time  in  the  history  of  the 
earth  w^hen  only  physical  forces  existed,  chemical  affinity 
being  held  in  abeyance  by  the  intensity  of  the  heat.*  By 
gradual  cooling,  chemical  affinity  at  a  certain  stage  came 
into  being — was  born,  a  new  form  of  force,  with  new  and 
peculiar  phenomena,  though  doubtless  derived  from  the 
preceding.  Ages  upon  ages  passed  away  until  the  time 
was  ripe  and  conditions  were  favorable,  and  life  appeared 
— a  new  and  higher  form  of  force,  jDroducing  a  still  more 
peculiar  group  of  phenomena,  but  still,  as  I  believe,  de- 
rived from  the  preceding.  Ages  upon  ages  again  passed 
away,  during  wdiich  this  life-force  took  on  higher  and 
higher  forms — in  the  highest  foreshadowing  and  simu- 
latinsf  reason  itself — until  finallv,  when  the  time  was 
fully  ripe  and  conditions  were  exceptionally  favorable, 
spirit,  self-conscious,  self-determining,  rational,  and 
moral,  appeared — a  new  and  still  higher  form  of  force, 
but  still,  as  I  am  persuaded,  derived  from  the  preceding. 
But  some  will  ask,  "  How  is  this  consistent  with  im- 
mortality ?  "  In  answer,  let  me  again  remind  the  reader 
that  with  every  new  form  of  force,  with  every  new  birth 
of  the  universal  energy  into  a  higher  plane,  there  appear 
new,  unexpected,  and,  previous  to  experience,  wholly  un- 
imaginable properties  and  powers.  This  last  birth  is  of 
course  no  exception.     Why  may  not  immortality  be  one 

*  All  chemical  compounds  are  dissociated  by  sufficient  heat. 


THE   RELATION  OF  MAN  TO  NATURE.         299 

of  these  new  properties  ?     But  this  j)oint  is  so  important 
that  we  must  treat  it  more  fully. 

Eemember,  then,  the  view  of  the  relation  of  God  to 
Nature,  already  ex|)lained.  Eemember  that  the  forces 
of  Nature  are  naught  else  than  different  forms  of  the 
one  omnipresent  Divine  energy.  Remember  that,  as  just 
shown,  this  Divine  omnipresent  energy  has  taken  on  suc- 
cessively higher  and  higher  forms  in  the  course  of  cosmic 
time.  Now  this  upward  movement  has  been  wholly  by 
increasing  individtuctlon,  not  only  of  matter,  but  also 
of  force.  This  universal  Divine  energy,  in  a  genei*alized 
condition,  tmincUviduated,  diffused,  pervading  all  Na- 
ture, is  what  we  call  physical  and  chemical  force.  The 
same  energy  in  higher  form,  individuating  matter,  and 
itself  individuated,  but  only  yet  very  imperfectly,  is 
what  we  call  the  life-force  *  of  plants.  The  same  energy, 
more  fully  individuating  matter  and  itself  more  fully  in- 
dividuated, but   not   completely,  we  call  the  anima  of 

*  I  knorr  it  is  the  fashion  to  ridicule  the  use  of  the  terms  vitality, 
vital  force,  as  a  remnant  of  an  old  superstition ;  and  yet  the  same  men 
who  do  so  use  the  terms  gravity,  electricity,  chemical  force,  etc.  Vital 
force  is  indeed  correlated  with  other  forces  of  Nature,  but  is  none  the 
less  a  distinct  form  of  force,  far  more  distinct  than  any  other  unless  it 
be  the  still  higher  form  of  psychical,  and  therefore  it  better  deserves  a 
distinct  name  than  any  lower  form.  Each  form  of  force  gives  rise  to  a 
peculiar  group  of  phenomena,  and  the  study  of  these  to  a  special  depart- 
ment of  science.  Xow,  the  group  of  phenomena  called  vital  is  more 
peculiar,  more  different  from  other  groups  than  these  are  from  each 
other,  and  the  science  of  physiology  is  a  more  distinct  department  than 
either  physics  or  chemistry,  and  therefore  the  form  of  force,  which  de- 
termines these  phenomena,  is  more  distinct  and  better  entitled  to  a  name 
than  any  physical  or  chemical  force. 


300       EVOLUTION  AND  RELIGIOUS  THOUGHT. 

animals.  This  anima,  or  auimal  soul,  as  time  went  on, 
was  individuated  more  and  more  until  it  resembled  and 
foreshadovv'ed  the  spirit  of  man.  Finally,  still  the  same 
energy,  completely  individuated  as  a  separate  entity,  and 
therefore  self-conscious ;  capable  of  separate  existence, 
and  therefore  immortal,  we  call  the  spirit  of  man. 

According  to  this  view,  the  vital  principle  of  plants 
and  the  anima  of  animals  are  but  different  stages  of  the 
development  of  spirit  in  the  womb  of  Xature  :  in  man 
at  last  it  came  to  hirth.  In  plants  and  animals  it  was  in 
deep  embryo  sleep — in  the  latter,  quickened,  indeed,  but 
not  viable — still  unconscious  of  self,  incapable  of  inde- 
pendent life,  with  physical,  umbilical  connection  with 
Mature  ;  but  now  at  last  in  man,  separated  from  Xature, 
capable  of  independent  life,  born  into  a  new  and  higher 
l">lane  of  existence.  Separated,  but  not  wholly ;  Xature 
is  no  longer  gestative  mother,  but  still  nursing  mother 
of  spirit.  As  the  organic  embryo  at  birth  reaches  inde- 
pendent material  or  temporal  life,  even  so  spirit  embryo 
by  birth  attains  independent  sjoiritual  or  eternal  life. 

Although  birth  is  its  truest  correspondence  and  best 
illustration,  yet  we  may  vary  the  illustration  in  many 
ways.  In  animals  spirit  is  deep  submerged  in  Nature  as 
beneath  a  water-surface,  wholly  unknowing  of  any  higher, 
freer  world  above.  In  man  sj)irit  emerges  above  the  sur- 
face into  a  higher  world,  looks  down  on  Nature  beneath 
him,  around  on  other  emerged  spirits  about  him,  and  up- 
ward to  the  Father  of  all  spirits  above  him.  Emerged 
but  not  wholly  free — head  above,  but  not  yet  foot-loose. 


THE   RELATION   OF   MAN   TO   NATCRE.         301 

Or,  again  :  As  a  planet  must  break  away  from  physi- 
cal, cohesive  connection  with  the  central  sun  (planet- 
birth)  in  order  to  enter  into  higher  gravitative  relations, 
which  thenceforward  determine  all  its  movements  in 
beautiful  harmony ;  as  the  embryo  must  break  away 
from  physical  umbilical  connection  with  the  mother 
in  order  to  enter  into  higher  spiritual  bonds  of  love, 
which  thenceforward  determine  all  their  mutual  rela- 
tions— even  so  s])iYit  must  break  away  from  physical  and 
material  connection  with  the  forces  of  Nature,  which 
are  but  the  omnipresent  Divine  energy,  in  order  there- 
by to  enter  into  higher  relations  of  filial  love  to  God  and 
brotherly  love  to  man.  Finally,  as  the  new-born  child 
differs  little  in  grade  of  physical  organization  from  the 
mature  but  unborn  embryo,  but  at  the  moment  of 
birth  there  is  a  sudden  and  complete  change,  not  so 
much  in  the  grade  of  organization  but  in  the  whole 
plane  of  existence — a  change  absolutely  necessary  for 
farther  advance,  for  another  cycle  of  life  ;  even  so  at 
the  moment  of  the  origin  of  man,  howsoever  this  may 
have  been  accomplished,  there  may  have  been  no  great 
change  in  the  grade  of  psycJiical  structure,  but  yet  a 
complete  change  in  the  /:>/«?ie  of  psychical  life — a  change 
absolutely  necessary  for  further  advance,  for  another 
cycle  of  evolution.  In  both  cases  there  is  a  sudden 
entrance  into  a  new  world,  the  sudden  appearance  of  a 
new  creature  with  entirely  different  capacities — a  pass- 
ing out  of  an  old  world,  a  waking  up  in  a  new  and 
higher.     According  to  this  view,  man  alone  is  a  child  of 


302       EVOLUTION   AND   RELIGIOUS   THOUGHT. 

God,  callable  of  separate  spirit-life — separate  but  not 
yet  wholly  independent  of  Nature.  As  already  said. 
Nature  is  no  longer  gestative  mother,  but  still  nursing 
mother  of  spirit — we  are  weaned  only  by  death. 

Or,  again  :  As  in  passing  up  the  organic  scale,  we 
find  all  grades  of  completeness  of  organic  individuality, 
an  increasing  individuation  of  bodily  form,  which  com- 
pletes itself  as  a  perfect  organic  individual  only  in  the 
higher  animals,  so,  also,  in  passing  up  the  dy7icunic  scale, 
force  or  energy  is  individuated  more  and  more  until 
the  process  reaches  completeness  as  a  spirit  individual  or 
dynamic  individual — a  person  only  in  man. 

The  more  we  reflect  on  this  subject,  the  more  we 
shall  be  convinced  that  completed  spirit-individuality 
explains,  as  nothing  else  can,  all  that  is  characteristic 
of  man.  It  is  this  which  constitutes  person,  or  the 
self-acting  ego.  It  is  this  which  constitutes  self-con- 
sciousness, free-will,  and  moral  responsibility.  And  out 
of  these  again  grow  the  recognition  of  relations  to 
other  moral  beings  and  to  God,  and  therefore  ethics  and 
religion.  Out  of  these,  also,  grow  the  capacity  of  indefi- 
nite voluntary  progi'ess.  This  also  means  separate  life, 
spirit-viability,  or  immortality.  Self-consciousness  espe- 
cially seems  to  me  the  simplest  sign  of  separate  entity  or 
spirit-individuality,  and  its  appearance  among  psychical 
phenomena  the  very  act  of  spirit-Mrtli.  We  may  imag- 
ine man  to  have  emerged  ever  so  gradually  from  ani- 
mals :  in  this  gradual  develoj^ment  the  moment  he  be- 
came   conscious    of    self,    the    moment    he    turned    his 


THE  KELATION  OF  MAN  TO  NATURE.    303 

thoughts  inward  in  wonder  upon  himself  and  on  the 
mystery  of  his  existence  as  separate  from  Xature,  that 
moment  marks  the  birth  of  humanity  out  of  animality. 
All  else  characteristic  of  man  followed  as  a  necessary 
consequence.  I  am  quite  sure  that,  if  any  animal,  say  a 
dog  or  a  monkey,  could  be  educated  up  to  the  point  of 
self-consciousness  (which,  however,  I  am  sure  is  imjios- 
sible),  that  moment  he  (no  longer  it)  would  become  a 
moral  responsible  being,  and  all  else  characteristic  of 
moral  beings  would  follow.  At  that  moment  would 
come  personality,  immortality,  capacity  of  voluntary 
progress ;  and  science,  philosoph}^,  religion  would  quick- 
ly follow. 

We  have  emphasized  self-consciousness  as  the  most 
fundamental  sign  of  spirit-individuality  ;  but  a  difference 
of  exactly  the  same  kind  is  found  running  through  the 
whole  gamut  of  human  faculties  as  compared  with  corre- 
sponding faculties  in  animals.  As  animal  consciousness 
is  related  to  human  self-consciousness,  so  exactly  is  ani- 
mal will  to  human  free  will,  animal  intelligence  to  hu- 
man reason,  animal  sign-language  to  rational  grammati- 
cal speech  of  man,  constructive  art  of  animals  to  true  ra- 
tional progressive  art  of  man.  In  every  one  of  these  the 
resemblance  is  great,  but  the  difference  is  immense,  and 
not  only  in  degree,  but  also  in  kind.  In  every  case  it  is 
like  shadow  and  substance,  projnise  and  fulfillment,  or, 
still  better,  it  is  like  embryo  and  child.  The  change 
from  one  to  the  other  is  like  to  a  birth  into  a  higher 
sphere,  the  beginning  of  another  cycle  of  evolution.     We 


304       EVOLUTION  AND  RELIGIOUS   THOUGHT. 

would  like  to  follow  this  idea  out  in  detail,  but  it  would 
lead  us  beyond  the  scope  of  this  work.  Those  who  desire 
to  do  so  we  would  refer  to  an  article  bv  the  author  on  the 
*^^  Psychical  Eelation  of  Man  to  Animals."  * 

Some  General  Conclusions. — There  are,  however,  two 
or  three  thoughts  so  closely  connected  with  what  we  have 
already  said  that  we  can  not  pass -them  over. 

1.  We  have  seen  that  every  mental  state  corresponds 
with  a  particular  brain  state,  and  every  mental  change 
with  a  brain  change.  We  have,  therefore,  here,  two 
series,  physical  and  psychical,  corresponding  with  each 
other,  term  for  term.  For  everv  chano;e  in  the  one  there 
is  a  corresponding  change  in  the  other,  both  in  kind  and 
amount.  Now,  is  not  this  the  test  of  the  relation  of 
cause  and  effect  ?  It  certainly  is.  Yes,  there  must  be 
a  causal  relation  here,  even  though  we  are  not  able  to 
understand  the  nature  of  the  causal  nexus.  But  which 
is  cause  and  which  effect  ?  If  the  view  above  presented 
be  correct,  then  in  animals  hrain  changes  are  in  all  cases 
the  cause  of  psychical  phenomena.  In  man  alone,  and 
only  in  his  higher  activities,  psychic  changes  precede 
and  determine  brain  changes.  In  man  alone  brain 
changes  are  determined  not  only  by  external  but  by 
internal  im^xQ&^ioi^^.  Man  alone  perceives  not  only  oh- 
JQcts—riiaferial  things — but  also  relations  and  properties 
abstracted  from  the  objects,  i.  e.,  ideal  things;  and, 
moreover,   not  only  relations  between  objects,   but  also 


*  "Princeton  Review"  for  May,  1884. 


THE   KELATION   OF  MAN   TO  NATURE.        305 

relations  between  relations  or  ideas.  In  man  alone 
there  is  an  inner  world  —  microcosm  —  the  things  of 
which  are  thoughts,  ideas,  etc.  This  self-acting  poiuer 
of  spirit  on  the  things  of  itself,  instead  of  merely  re- 
acting as  played  upon  by  external  nature,  is  charac- 
teristic of  man,  and  is  a  necessary  result  and  a  sign 
of  seyerance,  partial  at  least,  of  physical  bond  with 
Nature. 

2.  Again,  I  have  used  the  term  vital  principle.  I 
must  justify  it.  I  know  full  well  that  it  is  the  fashion 
to  ridicule  the  term  as  a  remnant  of  an  old  superstition 
which  regards  vital  force  as  a  sort  of  supernatural  entity 
unrelated  to  other  forces  of  Nature.  No  one  has  striven 
more  earnestly  than  myself  to  establish  the  correlation  of 
vital  with  physical  and  chemical  forces ;  and  yet,  if  the 
view  above  presented  be  true,  there  is  a  Jciiid  of  justifica- 
tion even  for  the  term  vital  principle — much  more,  vital 
force.  There  is  a  kind  of  reason  and  true  insight  in  the 
personification  of  the  forces  of  Nature,  and  especially  of 
vital  force.  All  forces,  by  progressive  dynamic  indi- 
viduation, are  on  the  way  toward  entity,  but  fully  attains 
that  condition  only  in  man. 

3.  Again,  to  perceive  relations  and  properties  ab- 
scracted  from  material  things,  to  form  abstract  or  general 
ideas,  to  form  not  only  percepts  but  also  cojicejtts,  is  ad- 
mitted to  be  a  characteristic  of  man — a  characteristic  on 
which  all  our  science  and  philosophy  rest.  From  time 
immemorial  the  vexed  question  has  been  debated,  "  Have 
such  abstract  or  general  ideas  any  real  existence,  or  are 


806       EVOLUTION  AND  RELIGIOUS  THOUGHT. 

they  mere  names  of  figments  of  the  mind?"  This  is 
the  famous  question  of  realism  and  nominalism.  Now, 
if  our  view  be  correct,  then  there  is  one  most  funda- 
mental abstraction,  viz.,  self,  which  is  indeed  a  realiti). 
Self-consciousness  is  the  direct  recognition  of  the  one 
reality,  spirit,  of  which  all  others  are  the  sign  and 
shadow — the  true  reality  which  underlies  and  gives  po- 
tency to  all  abstractions  or  ideas.  Do  we  not  find  in  this 
view,  then,  the  foundation  of  a  true  realism,  or  rather  a 
complete  reconciliation  of  realism  and  nominalism  ? 

4.  Thus,  then,  Nature,  through  the  whole  geological 
history  of  the  earth,  was  gestative  mother  of  spirit, 
which,  after  its  long  embryonic  development,  came  to 
birth  and  independent  life  and  immortality  in  man.  Is 
there  any  conceivable  meaning  in  Nature  without  this 
consummation  ?  All  CA'olution  has  its  beginning,  its 
course,  its  end.  Without  spirit-immortality  this  beauti- 
ful cosmos,  which  has  been  developing  into  increasing 
beauty  for  so  many  millions  of  years,  when  its  evolution 
has  run  its  course  and  all  is  over,  would  be  precisely  as  if 
it  had  never  been — an  idle  dream,  an  idiot  tale  signifying 
nothing.  I  repeat :  Without  spirit-immortality  the  cos- 
mos has  no  meaning.  Now  mark  :  It  is  equally  evident 
that,  ivitliout  this  gestative  method  of  creation  of  spirit, 
the  whole  geological  history  of  the  earth  previous  to  man 
would  have  no  meaning.  If  man's  spirit  were  made  at 
once  out  of  hand,  why  all  this  elaborate  preparation  by 
evolution  of  the  orsranic  kin2:dom  ? 

Thus,  again,  man  is  born  of  Nature  into  a  higher  na- 


THE  RELATION  OF  MAN  TO  NATURE.    307 

ture.  He  therefore  alone  is  possessed  of  two  natures — a 
lower,  in  common  with  animals,  and  a  higher,  peculiar 
to  himself.  The  whole  mission  and  life-work  of  man  is 
the  progressive  and  finally  the  complete  dominance,  both 
in  the  individual  and  in  the  race,  of  the  higher  over  the 
lower.  The  whole  meaning  of  sin  is  the  humiliating 
bondage  of  the  higher  to  the  lower.  As  the  material 
evolution  of  Nature  found  its  goal,  its  completion,  and 
its  significance  in  man,  so  must  man  enter  immediately 
upon  a  higher  sinritual  evolution  to  find  its  goal  and 
completion  and  its  significance  in  the  ideal  man — the 
Divine  man.  As  spirit,  unconscious  in  the  w^omb  of  Na- 
ture, continued  to  develop  by  necessarij  law  until  it  came 
to  birth  and  independent  life  in  man,  so  the  new-born 
spirit  of  man,  both  in  the  individual  and  in  the  race, 
must  ever  strive  by  freer  law  to  attain,  through  a  newer 
birth,  unto  a  higher  life. 


CHAPTER  V. 

THE   RELATIOJi   OF   GOD   TO    MAX. 

In"  the  two  preceding  chapters  we  have  discussed  the 
relation  of  God  to  Nature  and  of  man  to  Nature.  There 
is  still  another  relation,  if  possible,  of  still  more  vital  im- 
portance to  us,  viz.,  the  relation  of  God  to  man.  This, 
of  course,  introduces  the  question  of  revelation — a  sub- 
ject which  I  approach  with  some  reluctance.  I  feel  I  am 
treading  on  holj  ground,  and  must  do  so  with  shoes  re- 
moved. If  it  be  asked,  How  is  evolution  concerned 
with  the  subject  of  revelation  ?  I  answer  Evolution 
emphasizes  and  enforces  the  reign  of  law  taught  by  all 
science,  and  makes  it  at  last  universal.  Manv  conclude, 
therefore,  that,  if  evolution  be  true,  a  belief  in  the  possi- 
bility of  any  form  of  revelation  is  irrational.  I  do  not 
think  this  follows,  and  I  will  give  my  reasons.  I  do  so, 
however,  very  briefly,  because  we  are  not  yet  ready  to 
formulate  our  views  except  in  the  most  general  way. 

If  man  be  indeed  something  more  than  a  higher  spe- 
cies of  animal ;  if  man's  spii'it  be  indeed  a  spark  of  Di- 
vine energy  individuated  to  the  point  of  self-conscious- 
ness and  recognition  of  his  relation  to  God  ;  if  spirit- 


THE  RELATION  OF  GOD  TO  MAN.  309 

embryo,  developing  in  the  womb  of  Nature  through  all 
geological  time,  came  to  birth  and  independent  spirit-life 
in  man,  and  thus  man  alone  is  a  child  of  God  as  well  as  a 
product  of  Nature — if  all  this  be  true,  then  it  is  evident 
that  this  wholly  neiu  relation  requires  also  a  wholly  differ- 
ent mode  of  Divine  operation.  If  God  operates  on 
Nature  only  by  regular  j)rocesses,  Avhich  we  call  statural 
laius,  then  he  7mist  operate  on  spirit  in  a  different  and 
a  more  direct  way,  and  this  we  call  revelation.  If  to  the 
student  of  Nature  it  is  inconceivable  that  He  should 
operate  on  Nature  except  by  natural  law^s  (for  this 
is  the  name  we  give  to  His  chosen  mode  of  operation 
there),  then  to  the  student  of  theology  it  is  equally  incon- 
ceivable, if  our  view  of  man  be  true,  that  He  should  not 
operate  on  spirit  in  some  more  direct  and  higher  way, 
i.  e.,  by  revelation. 

But  some  will  ask,  Is  not  this  a  palpable  violation  of 
law  ?  I  think  not.  All  divine  operations  are,  must  be, 
according  to  reason,  i.  e.,  according  to  law.  The  opera- 
tion of  the  divine  on  the  human  spirit,  i.  e.,  revelation, 
must  therefore  be  according  to  law,  but  a  higher  law 
than  that  which  governs  Nature,  and,  therefore,  from  the 
point  of  view  of  Xature,  supernatural.  There  is  nothing 
wholly  unique  in  this.  Life  is  a  higher  form  of  force 
than  the  physical  and  chemical.  Life-phenomena  are 
therefore  super-physical,  and  if  we  confined  the  term 
Nature  to  dead  Nature  they  would  be  supernatural.  So 
the  free,  self-determined  acts  of  spirit  on  spirit,  even  of 
the  spirit  of  man  on  the  spirit  of  man,  much  more  of  the 


310       EVOLUTION   AXD  RELIGIOUS   THOUGHT. 

Spirit  of  God  on  the  spirit  of  man,  may  be  according 
to  law,  and  yet  from  the  natural  point  of  view  be  super- 
natural. It  is  true  that,  in  the  complex  of  phenomena, 
material  and  spiritual  inextricably  woven  together, 
which  go  to  make  up  human  life,  Science  must  ever 
strive  to  reduce  as  much  as  possible  to  material  laws,  for 
this  is  her  domain,  and  she  is  bound  to  extend  it ;  but,  if 
our  view  of  man  be  true,  there  will  always  remain  a 
large  residuum  of  phenomena — a  whole  world  of  phe- 
nomena— which  will  never  yield,  because  clearly  beyond 
her  domain.  Standing  on  the  lower  material  plane,  these 
phenomena  are  wholly  super-material,  and  therefore  in- 
comprehensible from  the  material  point  of  view.  We 
must  rise  and  stand  on  the  higher  plane  before  these  also 
are  reduced  to  law,  but  a  higher  law  than  that  operating 
on  the  lower  plane.  If,  therefore,  science  insists  on  ban- 
ishing the  supernatural  from  the  realm  of  Xature,  the- 
ology may  reasonably  insist  on  its  necessity,  in  this  sense, 
in  the  realm  of  morals  and  relidon. 

If,  then,  the  direct  influence  of  the  Sjoirit  of  God 
on  the  spirit  of  man  be  what  we  call  revelation,  then 
there  is  evidently  no  other  kind  of  revelation  jDossible  ; 
and,  furthermore,  such  revelation  is  given  to  all  men  in 
different  degrees.  It  is  given  to  all  men  as  conscience  ; 
in  greater  measure  to  all  great  and  good  men  as  clearer 
perception  of  righteousness  ;  in  pre-eminent  measure  to 
Hebrew  prophets  and  Christian  apostles  ;  but  supremely 
and  perfectly  to  Jesus  alone.  But  there  is,  and  in  the 
nature  of  things  there  can  be,  no  test  of  truth  but  rea- 


THE  KELATION^   OF  GOD   TO  MAX.  311 

son.  "We  must  fearlessly,  but  honestly  and  reverently, 
try  all  things,  even  revelations,  by  this  test.  We  must 
not  regard,  as  so  many  do,  the  spirit  of  man  as  the  pass- 
ive amanuensis  of  the  Spirit  of  God.  Eevelations  to  man 
mast  of  necessity  partake  of  the  imperfections  of  the 
medium  through  which  it  comes.  As  pure  water  from 
heaven,  falling  upon  and  filtering  through  earth,  must 
gather  impurities  in  its  course  differing  in  amount  and 
kind  according  to  the  earth,  even  so  the  pure  divine 
truth,  filtering  through  man's  mind,  must  take  imperfec- 
tions characteristic  of  the  man  and  of  the  age.  Such  fil- 
trate must  be  redistilled  in  the  alembic  of  reason  to 
separate  the  divine  truth  from  the  earthy  impurities. 


CHAPTER  VI. 

THE  objectio:n",  that  the  above  view  implies  pan- 
theism,  ANSWERED. 

It  will  be  observed  that  the  views  presented  in  the 
last  three  chapters  are  closely  connected  with  one  another, 
and  all  conditioned  on  the  *^  Relation  of  God  to  Nature," 
urged  in  Chapter  III.  Now  it  will  doubtless  be  objected 
to  this  view,  especially  as  applied  in  Chajoter  IV  on  the 
^'  Relation  of  Man  to  Nature,"  that  it  js  naught  else  than 
pure  pantheism  ;  that  it  destroys  completely  the  personal- 
ity of  Deity,  and  with  it  all  our  hopes  of  communion 
with  him,  and  all  our  aspirations  of  love  and  worship 
toward  him  ;  that,  according  to  this  "view,  God  becomes 
only  the  soul  or  animating  principle  of  Nature,  operat- 
ing everywhere  but  unconsciously  like  the  yital  principle 
of  an  organism  ;  that  the  whole  cosmos  becomes  in  fact  a 
great  organism,  developing  under  the  o^ieration  of  resi- 
dent  force  according  to  necessary  law,  only  that  ivc 
apotheosize  this  omnipresent  force  and  call  it  God  ;  and 
finally,  that  God  is  naught  else  than  an  abstraction, 
created  like  other  abstractions  or  general  ideas  wholly  by 
the   human   mind,  and   having   no   objective  existence. 


OBJECTIOiT  ANSWERED.  313 

Furthermore,  it  will  be  said,  that  according  to  this  view, 
this  omni2:)resent  unconscious  energy  individuates  itself 
by  necessary  law  of  evolution  more  and  more  until  it 
reaches,  for  the  Ji7'st  time  tn  man,  self-consciousness  and 
immortality,  and  thus  that  man  himself  is  the  only  self- 
conscious  immortal  being  in  existence,  and  therefore  the 
only  being  worthy  of  reverence  and  worship.  Thus,  this 
view  leads  to  humanity-worship  or  rather  to  self-ivorhM]). 
I  feel  the  full  force  of  this  objection.  I  answer  it  as 
follows  :  I  freely  admit  that,  following  up  this  scientific 
line  of  thought  alone,  we  are  carried  strongly  in  the  direc- 
tion of  pantheism.  But  there  is  nothing  strange  or  ex- 
ceptional in  this.  In  all  the  deepest  questions,  single 
lines  of  thought  inevitably  carry  us  to  extreme  one-sided 
views.  This  seems  to  be  the  necessary  result  of  the 
essentially  two-fold  nature  of  man,  self-conscious  spirit 
in  a  material  body,  the  relation  between  which  is,  and 
must  ever  be,  irtscrutable.  On  this  account  there  is  and 
must  be  a  fundamental  antithesis  in  human  philosophy, 
i.e.,  two  lines  of  thought,  the  material  and  spiritual,  which 
lead  to  two  apparently  irreconcilable  views.*  We  have 
already  seen  that  a  rational  philosophy,  whenever  we  are 
able  to  reach  such,  is  always  found  in  a  higher  and  more 
comprehensive  view,  which  includes,  combines,  and  rec- 
onciles two  one-sided,  partial,  and  mutually  excluding 
views.    But  spirit  and  matter,  or  mind  and  brain,  or  God 


*  For  a  fuller  statement  of  this  antithesis,  see  an  article  by  the  author 
entitled  "  Evolution  in  Relation  to  Materialism,"  "  Princeton  Review," 
for  March,  1881. 


314       EVOLUTION  AND  EELIGIOUS   THOUGHT. 

and  Nature,  is  the  fundamental  antithesis  which  underlies 
and  is  the  cause  of  all  other  lesser  antitheses.  This  anti- 
thesis, therefore,  is  absolutely  fundamental,  and  therefore 
forever  irreconcilable.  We  must  accept  both  sides,  even 
though  we  can  not  clearly  perceive  the  nature  of  their 
relation.  AYe  must  be  content  with  comj^romise  where 
we  can  not  effect  complete  reconciliation.  We  must 
frankly  acknowledge  that  the  antagonism  is  apparent 
only,  and  the  result  of  the  limitation  of  our  faculties, 
and  believe  that,  if  we  could  only  rise  to  a  high  enough 
point  of  view,  like  all  other  antitheses,  this  also  would 
disappear  in  a  rational  philosophy. 

Now,  to  apply  these  principles.  No  one,  we  admit, 
can  form  a  clear  conception  of  how  immanence  of  Deity 
is  consistent  with  personality,  and  yet  we  must  accept 
both,  because  we  are  irresistibly  led  to  each  of  these  by 
different  lines  of  thought.  Science,  following  one  line  of 
thought,  uncorrected  by  a  wider  philosophy,  is  naturally 
led  toward  one  extreme — i^antheistic  immanence  ;  the 
devout  worshiper,  following  the  wants  of  his  religious 
nature,  is  naturally  led  toward  another  extreme  of  anthro- 
pomorphic personality.  The  only  rational  view  is  to 
accept  both  immanence  and  personality,  even  though  we 
can  not  clearly  reconcile  them,  i.  e.,  immanence  without 
pantheism,  and  personality  without  anthropomorphism. 
AVe  have  already  seen  in  the  third  chapter,  how  follow- 
ing the  scientific  line  of  thought,  we  are  logically  driven 
to  immanence.  We  wish  now  to  show  how,  following  an- 
other line  of  thought,  we  are  as  logically  driven  to  per- 


OBJECTIOX  ANSWERED.  315 

Gonality.  On  this  most  difficult  subject,  howevGr,  all  we 
are  prepared  to  do  is  to  throw  out  some  brief  suggestions, 
in  the  hope  that  they  may  be  carried  out  more  perfectly  by 
some  thoughtful  reader  ;  scatter  some  seed- thoughts,  in 
the  hope  that,  falling  haply  on  good  soil,  they  may  spring 
up  and  bear  more  fruit  than  I  have  been  able  to  produce. 

1.  In  the  gradual  individuation  of  the  universal  Di- 
vine energy  described  in  Chapter  IV,  there  must  of  course 
be  a  corresponding  growth  of  a  kind  of  independent  self- 
activity  which  reaches  completeness  in  man,  and  in  fact 
constitutes  what  we  call  self-consciousness  and  free  will. 
The  exact  nature  of  the  relation  of  Deity  or  of  the  gen- 
eral forces  of  Nature  to  this  gradually  individuated  por- 
tion, I  do  not  undertake  to  define.  And  how  this  idea  of 
partial  self-activity  comports  with  the  absoluteness  of 
Deity  we  can  not  clearly  understand.  But  this  fact  need 
not  specially  disturb  us  here  ;  for  this  is  only  one  branch 
of  the  wider  question  of  the  moral  agency  of  man  in  rela- 
tion to  the  absolute  sovereignty  of  God,  or  the  freedom 
of  man  in  relation  to  necessary  law  in  J^ature. 

2.  We  have  already  shown  that,  if  the  brain  of  a  living, 
thinking  man  were  exposed  to  the  scrutiny  of  an  out- 
side observer  with  absolutely  perfect  senses,  all  that  he 
would  or  could  possibly  see  would,  be  molecular  motions, 
physical  and  chemical.  But  the  subject  himself,  the 
thinking,  self-conscious  spirit,  would  experience  and  ob- 
serve by  introspection  only  consciousness,  thought,  emo- 
tion, etc.  On  the  outside,  only  physical  phenomena ; 
on  the   inside  only  psychical  phenomena.     Now,  must 


316       EVOLUTION   AND   RELIGIOUS   THOUGHT. 

not  the  same  he  necessarily  true  of  Nature  also  ?  Viewed 
from  the  outside  by  the  scientific  observer,  nothing  is 
seen,  nothing  can  be  seen,  there  is  nothing  else  to  be 
seen,  but  motions,  material  phenomena ;  but  behind 
these,  on  the  other  side,  on  the  inside,  must  not  there 
be  in  this  case  also  psychical  i:)henomena,  conscious- 
ness, thought,  will;  in  a  word,  personality?*  In  the 
only  place  w4iere  we  do  get  behind  physical  phenomena, 
viz.,  in  the  brain,  w^e  find  psychical  phenomena.  Are 
we  not  justified,  then,  in  concluding  that  in  all  cases 
the  psychical  hes  behind  the  physical  ?  The  human 
brain  is  a  wonderful  instrument,  by  means  of  which,  in 
some  inscrutable  way,  viz.,  in  our  own  experience,  we  do 
get  behind,  on  the  other  side,  on  the  inside  of  some  mate- 
rial phenomena,  and  in  so  far  become  partakers  of  the 
Divine  nature.  But  behind  other  phenomena  of  Nature 
we  may  never  hope  to  penetrate  either  by  observation  or 
experience,  but  only  in  dim  way  by  highest  reason.  Sci- 
ence, even  in  the  case  of  the  brain,  can  not  pass  from  the 
one  kind  of  phenomena  to  the  other.  If  she  would  study 
the  inside  she  must  abandon  the  outside — she  must  aban- 
don the  microscope  and  take  to  introspection.  If  she 
would  study  the  phenomena  of  the  higher  platform,  she 
must  leave  the  low^r  and  climb  up  and  stand  on  the 
hisfher.  If  this  be  true  of  the  brain  where  the  two  kinds 
of  phenomena  are  brought  so  close  together,  how  much 
more  is  it  true  of   the  phenomena  of  the  cosmos.     AVe 

*  Johnstone,  "  Stoncy-Nature,"  vol.  xxxi,  p.  422. 


OBJECTION   ANSWERED.  317 

can  never  hope,  either  by  observation  or  by  experience,  to 
pass  beyond  the  veil.  We  must  abandon  the  methods  of 
science  and  reach  it,  if  at  all,  in  some  other  way.  Not 
the  clear-sighted  but  the  pure-hearted  shall  see  God. 

In  the  light  of  what  is  said  above,  it  is  almost  amus- 
ing to  see  how  persistently  some  writers  try  to  expel 
mind  from  Nature,  while  others  as  anxiously  strive  to 
retain  for  mind  at  least  some  small  corner,  especially  as 
one  of  the  causes  or  factors  of  evolution.*  Both  sides 
wholly  misconceive  the  matter,  although  the  former  are 
more  consistent.  One  of  the  causes  !  Mind  is  either  all 
or  none  ;  so  also  mechanics  is  all  or  none.  It  is  all  mind 
through  mechanics.  It  is  all  mechanics  from  the  outside, 
and  it  is  all  mind  from  the  inside.  For  science  it  is  all  me- 
chanics, for  theology  it  is  all  mind.  It  is  the  duty  of 
philosophy  to  reconcile  these  two  opposite  views.  In  one 
form  of  evolution  only,  viz.,  in  human  progress,  is  mind 
one  of  the  factors  of  evolution.  But  to  think  and  speak 
thus  of  God  in  relation  to  Nature  is  to  place  him  on  the 
human  plane. 

Thus,  then,  we  see  that  our  own  self-conscious  person- 
ality behind  brain  phenomena  compels  us  to  accept  con- 
sciousness, will,  thought,  personality  behind  Nature.  Now 
I  assert  that  once  get  this  abstract  idea  in  the  mind,  and 
by  a  necessary  law  of  thought  it  gradually  expands 
without  limit,  and  eventuallv  reaches  the  form  of  infinite 
consciousness,  will,  thought,  etc.,  and  therefore  of  an  in- 

*  See  "  Nature,"  vol.  xxxiv,  pp.  355  and  385,  18S6. 


318       EVOLUTION   AND   RELIGIOUS  THOUGHT. 

finite  person.  This  law  of  indefinite  expansion  may  be 
illustrated  by  the  ideas  of  space  and  time.  The  animal, 
and  indeed  the  infant,  understands  space  and  time  only 
in  their  relation  to  itself,  but  has  not  yet  abstracted  these 
from  their  contents.  This  comes  only  with  the  birth  of 
self-conscious  personality.  But,  so  soon  as  the  abstract 
idea  of  space  is  acquired,  by  a  necessary  law  of  mental 
activity  it  expands  without  limit,  and  finally  becomes 
the  idea  of  infinite  space.  Similarly,  so  soon  as  the  idea 
of  time  as  abstracted  from  its  contents  is  conceived,  it 
inevitably  expands  without  limit  and  grows  into  the 
idea  of  infinite  time.  So  is  it  precisely  with  the  idea  of 
self-conscious  personality.  The  animal  or  the  very  young 
child  is  indeed  conscioas  of  its  body  and  of  external 
objects  in  their  mutual  relations,  but  not  of  self,  as  ab- 
stracted from  its  contents.  The  animal  never  attains  it, 
the  child  does,  l^ow,  so  soon  as  this  idea  of  self-con- 
scious personality — of  a  spiritual  entity  underlying  mate- 
rial phenomena — appears,  by  a  necessary  law  of  mental 
activity  it  expands  without  limit,  and  inevitably  reaches 
the  idea  of  an  infinite  self,  an  infinite  person,  God,  be- 
hind the  phenomena  of  Nature. 

But  some  will  object  that  this  idea  of  infinite  person- 
ality is  inconceivable.  True  enough,  but  the  opposite  is 
far  more  inconceivaUe.  The  ideas  of  infinite  space  and 
infinite  time  are  also  inconceivable,  yet  we  must  accept 
them,  because  the  idea  of  all  space  or  all  time  being  lim- 
ited is  still  more  inconceivable  ;  for  if  we  think  of  space 
or  time  as  limited,  immediately  there  comes  the  ques- 


OBJECTIOiT  ANSWERED.  319 

tion,  'MVliat  is  there  beyond  the  limit?"  There  is 
therefore  this  wide  difference  between  these  two  in- 
conceivables  :  the  one  is  so  only  in  the  sense  of  tran- 
scending the  power  of  our  mind,  but  the  other  is  un- 
thinkable, self-colitradictory,  absurd.  So  also  is  it  with 
self-conscious  personality.  The  idea  of  an  infinite  self, 
i.  e.,  God,  is  indeed  inconceivable,  but  only  in  the  sense  of 
transcending  our  power  of  comprehension  ;  but  the  idea 
of  the  consciousness  behind  the  cosmos  as  being  limited 
or  finite  is  more  than  inconceivable,  it  is  unthinkable, 
self-contradictory,  absurd  ;  for  immediately  comes  the 
question,  '^  What  is  there  beyond  which  limits  it  ?"  To 
the  Greek  mind  Zeus  was  limited,  therefore  of  necessity 
came  also  the  idea  of  Fate,  superior  to  and  limiting  Zeus 
himself.  To  them,  therefore.  Fate  was  the  real  God — 
the  absolute. 

3.  We  have  thus  far  spoken  only  or  principally  of 
self-consciousness,  but  the  same  precisely  is  true  of  an- 
other essential  attribute  of  personality,  viz.,  free  will. 
Every  one  admits  causative  force  or  forces  operating  in 
Nature.  Science  has  shown  that  all  the  different  kinds 
of  force  are  but  different  forms  of  one  omnipresent 
energy.  Now,  looking  abroad  on  Nature  from  the  out- 
side, this  omnipresent  energy  seems  to  modern  science  as 
simply  resident,  inherent  in  matter  itself,  and  therefore 
as  operating  unconsciously  and  by  necessity.  But  the 
question  occurs,  "  Whence  did  we  get  the  idea  of  force, 
energy,  causation  V  I  answer  unhesitatingly  :  We  get 
it  not  from  without  by  observation  of  Nature,  but  from 
15 


320       EVOLUTION   AND   RELIGIOUS   THOUGHT. 

within  through  consciousness  ;  not  from  the  outside  view, 
but  from,  the  inside  yiew  of  phenomena.  We  can  not 
conceive  of  phenomena  without  force,  of  effects  without 
cause,  because  we  are  intensely  conscious  of  being  our- 
selves through  our  wills  an  active  cause  of  external  phe- 
nomena. If  we  were  merely  passive  observers,  not  ac- 
tive causers  of  changes  in  the  external  world,  tlien  these 
external  phenomena  would  seem  to  us  merely  to  shift 
and  change  and  succeed  each  in  a  certain  order.  AVe 
misfht  note  the  order  and  determine  the  laws  of  se- 
quence,  and  thus  form  a  science  ;  but  it  would  never 
enter  into  our  minds  to  imagine  any  causal  or  dynamical 
nexus  between  them.  In  the  mind  of  such  passive  ob- 
server, but  not  doer — thinker,  but  not  worker — would 
be  completely  realized  the  only  thorough-going  and  con- 
sistent materialistic  philosophy,  i.  c.,  a  philosophy  in 
which,  like  Comte's,  cause  and  force  have  no  place — are 
in  fact  banished  as  a  superstition  from  science.  But 
the  clear  consciousness  of  essential  energy,  of  causative 
force  within,  the  certainty  that  we  ourselves,  through 
our  wills  and  by  the  conscious  exertion  of  force  do  de- 
termine changes  in  the  external  world,  compels  us  to 
attribute  all  changes  to  causative  force  of  some  kind, 
and  naturally  enough,  until  the  interference  of  science, 
to  a  personal  will  like  our  own.  Thus  by  a  necessary 
law  we  project  our  internal  states  into  external  Nature. 
But  see  now  the  steps  of  evolution  of  this  idea.  At 
first,  i.  e.,  in  the  uncultured  races,  and  also  in  childhood, 
external  forces  take  the  form  of  a  personal  will  like  our 


OBJECTIOE"   ANSWERED.  321 

own  residing  in  each  object,  and  controlling  its  phenom- 
ena as  our  wills  control  our  bodily  movements  (fetich- 
ism).  Then,  as  culture  advances,  it  takes  next  the  form 
of  several  personal  wills  controlling  each  the  phenom- 
ena of  a  different  department  of  Nature  (polytheism). 
Finally,  in  the  highest  stage  of  culture,  it  takes  the 
form  of  one  personal  will  controlling  the  phenomena  of 
the  whole  cosmos  (monotheism).  To  the  religious  but 
unscientific  mind  in  all  these  stages  the  personal  will  is 
anthropomorjbhic.  But  we  have  already  seen  (Chapter 
III)  how  anthropomorphism  has  been  driven  by  science 
from  one  department  after  another,  until  now  at  last 
by  evolution  it  is  driven  out  of  Nature  entirely,  and 
to  those  following  this  line  of  thought  alone,  the  phe- 
nomena of  Nature  are  relegated  to  forces  inherent  in 
matter,  and  operating  by  laws  necessary  and  fatal ;  and 
not  only  so,  but  material  forces  are  made  to  invade 
even  the  realm  of  consciousness,  and  reduce  this  also  to 
material  laws.  Thus  the  savage  ejects  his  own  conscious 
personal  will  into  every  separate  object  of  Nature  ;  the 
modern  materialist  ejects  material  forces  into  the  realm 
of  consciousness..  But,  as  already  seen,  a  rational  phi- 
losophy admits  these  two  antithetic  views,  and  strives  to 
combine  and  reconcile  them.  This  reconciliation,  as  far 
as  it  is  possible  for  us,  is  found  in  a  personal  will  im- 
manent in  Nature,  and  determining  directly  all  its 
phenomena. 

Thus  it  is  evident  that  the  idea  of  a   causal  nexus 
between  successive  phenomena  is  a  primary  conception, 


322       EVOLUTION  AND   PwELIGIOUS  THOUGHT. 

and  therefore  ineradicable  and  certain.  Even  from  the 
purest  evolution  point  of  view  it  must  be  true,  for,  if 
man's  mind  grew  out  of  the  forces  of  Nature,  this  idea 
must  represent  a  fact  in  Xature.  Also,  analysis  shows 
that  all  causative  force  originates  in  luill.  Lastly,  cul- 
ture and  reason,  by  a  necessary  law  of  expansion,  car- 
ry us  uj^ward  to  the  conception  of  one  infinite  sus- 
taining and  creative  will.  Science  may  sometimes  ob- 
scure but  can  not  destroy  this  idea.  Evolution,  which 
was  supposed  by  some  to  have  destroyed  it  for  ever,  has 
only  temporarily  obscured  it  in  the  minds  of  the  unre- 
flecting, by  the  supposed  identity  of  evolution  with 
materialism.  From  this  tem2:)orary  eclipse  it  now 
emerges  with  still  greater  clearness  and  far  greater  no- 
bleness. For,  observe  :  All  the  effects  known  to  us  in 
Nature  are  finite  ;  therefore  a  personal  will,  which  deter- 
mines these  separately  by  successive  acts,  as  we  do,  must 
also  be  finite  like  ourselves.  But  a  will,  which  bv  one 
eternal  act  ever-doing,  never  done,  determines  the  evolu- 
tion and  the  sustentation  of  an  infinite  cosmos,  must  it- 
self  be  infinite.  Thus  onlv  in  the  doctrine  of  universal 
evolution  do  we  rise  to  a  just  conception  of  God  as  an  in- 
finite cause. 

4.  As  the  idea  of  cause  and  force  is  related  to  loill, 
so  precisely  is  the  idea  of  design  related  to  tliouglit.  We 
get  this  also,  not  from  without,  but  from  within.  Adap- 
tation of  means  to  ends  is  in  our  experience  the  result  of 
thought,  and  we  can  not  conceive  it  to  result  otherwise. 
The  effect  of  science  can  not  be  to  destroy  this  primary 


OBJECTION   ANSWERED.  323 

conception — wliicli,  indeed,  like  all  primary  conceptions, 
is  ineradicable,  and  already  more  certain  than  anything 
can  be  made  by  proof — but  only  to  exalt  and  purify  our 
conceptions  of  the  Designer.  For,  observe  :  In  any  case 
of  adaptive  structure,  whether  in  the  animal  body  or  in 
planetary  relations,  the  evidence  of  design  is  not  in 
the  materials,  but  in  the  use  of  the  materials  ;  not  in  the 
parts,  but  in  the  adjustment  of  the  parts  for  a  purpose. 
Design,  purpose,  adjustment,  adaptation,  are  not  ma- 
terial things,  but  relations  or  intellectual  things,  and 
therefore  perceivable  only  by  thought,  and  conceivable 
only  as  the  result  of  thought.  It  is  simply  impossible 
to  talk  about  such  adaptive  structures  without  using  lan- 
guage which  implies  design.  The  very  word  ^^  adaptive  " 
implies  it.  It  is  impossible  even  to  think  of  such  struct- 
ures without  implicitly  assuming  intelligence  as  the 
cause.  It  makes  no  particle  of  difference  lioio  the  mate- 
rial originated,  or  whether  it  ever  originated  at  all ;  it 
matters  not  whether  the  adaptation  was  done  at  once  out 
of  hand,  or  whether  by  slow  process  of  modification  ;  it 
matters  not  whether  the  adaptive  modification  was 
brought  about  by  a  process  of  natural  selection,  or  by 
pressure  of  a  physical  environment ;  whether  without  law 
or  according  to  law.  The  removal  of  the  result  from  man- 
like directness  of  separate  action  can  not  destroy  the  idea 
of  design,  but  only  modify  our  conception  of  the  Designer. 
What  science,  and  especially  evolution,  destroys,  there- 
fore, is  not  the  idea  of  design,  but  only  our  low  anthropo- 
morphic notions  of  the  mode  of  working  of  the  Designer. 


324      EYOLUTION   AND   RELIGIOUS  THOUGHT. 

Precisely  the  same  change  takes  place  here  under  the 
influence  of  science  as  has  taken  place  in  all  our  notions 
concerning  God.  The  uncultured  savage  sees  a  separate 
god  in  every  object.  As  culture  advances,  his  gods  be- 
come fewer  and  nobler,  until,  in  the  most  advanced 
states,  man  recognizes  but  one  infinite  God,  the  creator 
and  sustainer  of  all.  God  is  still  in  every  phenomenon, 
but  no  longer  as  a  separate  God,  but  only  as  the  sepa- 
rate manifestation  of  the  One.  Thus  culture  takes  away 
our  gods,  but  only  to  compel  us  to  seek  him  in  nobler 
forms  until  we  reach  the  only  true  God.  But,  even  after 
the  conception  of  the  one  God  is  reached,  how  many 
seem  to  regard  him  as  altogether  such  a  one  as  our- 
selves ;  but  science  shows  us  that  his  ways  are  not  like 
our  ways,  nor  his  ends  as  our  ends.  Thus  science, 
more  than  all  other  kinds  of  culture,  simplifies  while  it 
infinitely  ennobles  and  purifies  our  conceptions  of  Deity. 

Again,  the  same  change  takes  place  in  our  sense  of 
mystery.  I  suppose  most  people  imagine  that  it  is  the 
special  mission  of  science  to  destroy  all  mystery.  Many 
seem  to  think  that  superstition,  or  even  religion,  is  in- 
separably connected  with  ignorance  and  mystery,  and  all 
must  disappear  together  before  the  light  of  science. 
But  not  so.  There  is  only  a  gradual  progressive  change 
— an  evolution  in  the  form  of  myster}^  as  well  as  in  the 
form  of  religion.  To  the  savage  everything  is  a  sepa- 
rate mystery.  The  function  of  science  is,  indeed,  to 
destroy  tliese  separate  mysteries,  by  explaining  them  ; 
but,  in  doing  so,  it  only  reduces   them  to   fewer  and 


OBJECTION  ANSWERED.  325 

grander  mysteries,  and  these  again  to  still  fewer  and 
grander,  until,  in  an  ideally  perfect  science,  all  separate 
and  partial  mysteries  are  swallowed  up  in  the  one  all- 
embracing  infinite  mystery — the  mystery  of  existence. 
There  is  still  mystery  in  each  object,  but  no  longer  a 
separate  mystery — only  a  separate  manifestation  of  the 
one  overwhelming  mystery. 

Or,  again,  and  finally  :  The  same  change  occurs  in 
our  ideas  of  creation.  At  first  every  object  is  a  separate 
creation — a  manufacture.  With  advancing  science  these 
separate,  creative  acts  become  fewer  and  nobler,  until 
now,  at  last,  in  evolution,  all  are  embraced  and  swallowed 
up  in  one  eternal  act  of  creation — a  never-ceasing  pro- 
cession of  the  divine  energy.  Every  object  is  still  a 
creation,  but  not  a  separate  creation — only  a  separate 
manifestation  of  the  one  continuous  creative  act. 

Now,  precisely  the  same  change  must  take  i^lace  in 
onr  conception  of  design  in  Nature.  To  the  uncultured 
there  is  a  distinct  and  separate  design  in  every  separate 
w^ork  of  Nature.  But,  as  science  advances,  all  these 
distinct,  separate,  petty,  man-like  designs  are  merged 
into  fewer  and  grander  designs,  until,  finally,  in  evolu- 
tion at  last,  we  reach  the  conception  of  the  one  infinite, 
all-embracing  design,  stretching  across  infinite  space,  and 
continuing  unchanged  through  infinite  time,  wiiich  in- 
cludes and  predetermines  and  absorbs  every  possible 
separate  design.  There  is  still  design  in  everything,  but 
no  longer  a  separate  design — only  a  separate  manifesta- 
tion of  the  one  infinite  design. 


326       EVOLUTION   AND   RELIGIOUS   THOUGHT. 

Thus,  then,  our  own  self-consciousness  and  will  and 
thought  give  rise,  necessarily,  to  the  conception  of  an 
infinite  self-consciousness,  will,  and  thought — i.  e.,  God. 
The  necessity  to  believe  in  self-conscious  spirit  behind 
bodily  phenomena  compels  us  to  believe  also  in  an  infi- 
nite self-conscious  spirit  behind  cosmic  phenomena. 
Looking  at  the  operations  of  this  ever-active  spirit,  wheth- 
er in  the  one  case  or  the  other,  from  the  outside,  it  looks 
like  unconscious  energy  inherent  in  matter  itself,  and 
therefore  like  necessity,  or  fate.  But,  looked  at  from  the 
inside  in  the  one  case,  we  perceive  only  self-conscious, 
free  activity  of  spirit.  Therefore,  we  are  compelled  to 
acknowledge  in  the  other  case,  also,  the  same  source  of 
all  activity,  the  same  cause  of  all  phenomena.  We  are 
compelled  to  acknowledge  an  infinite  immanent  Deity 
behind  phenomena,  but  manifested  to  us  on  the  outside 
as  an  all-pervasive  energy.  But  some  portion  of  this  all- 
pervasive  energy  again  individuates  itself  more  and 
more,  and  therefore  acquires  more  and  more  a  kind  of 
independent  self-activity  which  reaches  its  completeness 
in  man  as  self-consciousness  and  free  will.  We  said,  '^  a 
Z;i;i<:/ 0/ independent  self-activity."  How  this  comports 
with  the  absoluteness  of  God  we  can  not  understand,  any 
more  than  we  can  understand  how  it  comports  with 
invariable  law  in  Nature.  We  simply  accept  them  both 
as  primary  truths,  even  though  we  can  never  hope  to  rec- 
oncile them  completely,  because  we  can  not  understand 
the  exact  nature  of  the  relation  of  spirit  to  matter.  We 
can  not  look  at  the  outside  and   the  inside  at  the  same 


objectio:n"  answered.  327 

time.  If  we  could  understand  the  relation  of  psychical 
phenomena  to  brain-changes,  then  might  we  hope  to 
understand  far  more  perfectly  than  now  the  relation  of 
God  to  Nature.  But  as  in  the  one  case,  the  brain,  al- 
though we  can  not  understand  the  nature  of  the  relation, 
yet  we  are  sure  of  the  intimacy  of  the  connection  of  the 
two  series,  psychical  and  physical,  term  for  term  ;  so  in 
the  other  case,  the  cosmos,  although  we  can  not  under- 
stand the  exact  nature,  we  are  sure  of  the  intimacy  of  the 
connection,  term  for  term — every  material  phenomenon 
and  event  with  a  corresponding  psychical  phenomenon  as 
its  cause. 


CHAPTER  VII. 

THE  RELATION  OF  EVOLUTIOi^  TO   THE   PROfeLEM  OF  ETIL. 

The  problem  of  evil  has  tasked  the  power  and  baffled 
the  skill  of  the  greatest  thinkers  in  every  age.  It  would 
be  folly  in  me  to  imagine  that  I  can  solve  it.  Its  com- 
plete solution  is  probably  impossible  in  the  jiresent  state 
of  science.  Yet  I  can  not  doubt  that  on  this,  as  on  every 
important  question  relating  to  man,  the  theory  of  evolu- 
tion will  throw  new  and  important  light.  All  I  can  hope 
to  do  is  to  throw  out  some  brief  suggestions  on  the  sub- 
ject. 

If  evolution  be  true,  and  especially  if  man  be  indeed 
a  product  of  evolution,  then  what  w'e  call  evil  is  not  a 
unique  phenomenon  confined  to  man,  and  the  result  of 
an  accident,  but  must  be  a  great  fact  pervading  all  na- 
ture, and  a  part  of  its  very  constitution.  It  must  have 
existed  in  all  time  in  different  forms,  and  subject  like 
all  else  to  the  law  of  evolution.  Let  us,  then,  trace  rap- 
idly some  of  the  steps  of  this  evolution. 

1.  External  Physical  Evil  in  the  Animal  Kingdom. 
— As  already  seen  in  previous  chapters,  the  necessary 
condition  of  evolution  of  the  organic  kingdom  is  a  strug- 


EVOLUTION  AND   THE   PROBLEM   OF   EVIL.    329 

gle  for  life — a  conflict  on  every  side,  with  a  seemingly 
inimical  environment  and  a  survival  of  only  the  strong- 
est, the  swiftest,  or  the  most  cunning — in  a  word,  the 
fittest.  Now,  suppose  the  course  of  organic  evolution 
finished  in  the  introduction  of  man,  and  from  this  vant- 
age-ground we  look  back  over  the  course  and  consider 
its  result.  Shall  we  call  that  evil  which  was  the  neces- 
sary condition  of  the  progressive  elevation  which  cul- 
minated so  gloriously  ?  Evil  doubtless  it  seemed  to  the 
individual,  struggling  animal,  but  is  this  worthy  to  be 
weighed  in  comparison  with  the  evolution  of  the  whole 
organic  kingdom  until  it  culminated  in  man  ?  Is  it  not 
rather  a  good  in  disguise  ?  I  suppose  human  arrogance 
may  be  willing  enough  to  admit  it  in  this  case,  where 
animals  only  are  sufferers. 

2.  Physical  Evil  in  Relation  to  Man. — But  organic 
evolution,  completed  in  man,  was  immediately  trans- 
ferred to  a  higher  plane,  and  continued  as  social  evolu- 
tion ;  material  evolution  is  transformed  into  psychical 
evolution  ;  unconscious  evolution,  according  to  neces- 
sary law,  to  conscious  voluntary  progress  toward  a  rec- 
ognized goal,  and  according  to  2^  freer  law.  But  in  this 
transformation  the  fundamental  conditions  of  evolution 
do  not  change.  Man  also  is  surrounded  on  every  side 
with  what  at  first  seems  to  him  an  evil  environment, 
against  which  he  must  ever  struggle  or  perish.  Heat 
and  cold,  tempest  and  flood,  volcanoes  and  earthquakes, 
savage  beasts  and  still  more  savage  men.  What  is  the 
remedy — the  only  conceivable  remedy  ?     Knowledge  of 


330       EVOLUTION   AND  RELIGIOUS  THOUGHT. 

the  laws  of  Nature,  and  tliereby  acquisition  of  power 
over  Nature.  But  increasing  knowledge  and  power  are 
equivalent  to  progressive  elevation  in  the  scale  of  psychi- 
cal being.  This  conflict  witli  what  seems  an  evil  en- 
vironment is,  therefore,  the  necessary  condition  of  such 
elevation.  It  is  not  too  much  to  say  that,  without  this 
condition,  except  for  this  necessity  for  struggle,  man 
could  never  have  emerged  out  of  animality  into  human- 
ity, or,  having  thus  emerged,  would  never  have  risen 
above  the  lowest  possible  stage.  Now  sujopose,  again, 
this  ideal  to  have  been  attained — suppose  knowledge  of 
physical  laws  and  power  over  physical  forces  to  be  com- 
plete— suppose  physical  nature  completely  subdued,  put 
beneath  our  feet,  and  subject  to  our  will,  and,  from  the 
high  intellectual  position  thus  attained,  we  look  back 
over  the  wiiole  ground  and  consider  the  result.  Shall 
that  be  called  evil  which  was  obviously  the  necessary 
condition  for  attaining  our  then  elevated  position  ? 
Evil  it  doubtless  seemed  to  the  individuals  who  fell, 
and  still  seems  to  us  who  now  suffer,  by  the  way  in 
the  conflict ;  but  is  physical  discomfort  or  even  physical 
death  of  the  individual  to  be  weighed  in  comparison 
with  the  ps3Thical  elevation  of  the  individual,  and  espe- 
cially of  the  race  ?  Evidently,  then,  physical  evil  even 
in  the  case  of  man  is  only  seeming  evil,  but  real  good. 
3.  Organic  Evil — Disease. — But  there  is  a  more 
dreadful  form  of  evil  than  that  which  results  from  ex- 
ternal physical  nature — an  evil  far  more  subtle  and  diffi- 
cult to  understand,  and  therefore  to  conquer.     I  mean 


EVOLUTION  AND   TPIE   PROBLEM   OF  EVIL.    331 

internal  organic  evil — disease  in  its  diversified  forms  and 
with  its  attendant  weakness  and  suffering,  inscrutable 
often  in  its  causes,  insidious  in  its  approaches,  conta- 
gious, infectious,  spreading  from  house  to  house,  carry- 
ing suffering  and  death  in  its  course,  and  leaving  sorrow 
and  desolation  behind.  Is  there  any  remedy  which  can 
transmute  this  evil  into  good  ?  There  is.  It  is  again 
knowledge—knowledge  of  the  laws,  and  power  over  the 
forces,  of  organic  nature.  Is  it  not  evident  that  complete 
knowledge  of  the  laws  of  health  and  the  causes  of  dis- 
ease would  put  this  evil  also  under  our  feet  ?  Is  it  not 
evident  that  a  perfect  knowledge  of  the  laws  of  health, 
and  a  perfect  living  according  to  these  laws,  would  so 
entirely  subdue  this  evil  that  men  would  no  longer  die 
except  by  natural  decay  or  by  accident  ?  Is  it  not  evi- 
dent, also,  that  the  race  will  not  attain  this  knowledge 
unless  it  be  forced  upon  us  by  the  necessity  of  avoiding 
the  dread  evil  of  disease  ? 

Now  suppose,  again,  this  ideal  attained,  suppose  this 
dread  evil  subdued  by  complete  knowledge,  and  again 
from  our  elevated  intellectual  position  we  look  back  over 
the  ground.  Shall  we  call  that  evil  which  was  the  ne- 
cessary condition  of  our  intellectual  elevation  ?  Evil, 
doubtless,  it  seems  to  us  individuals  who  have  suffered 
and  are  still  suffering  through  our  ignorance  ;  but  is 
such  individual  suffering  or  even  individual  death  to 
be  weighed  against  the  psychical  elevation  of  the  in- 
dividual and  evolution  of  the  race  ?  Ought  not  the 
individual  to  be  willins:  to  suffer  thus  much  vicarious- 


332       EVOLUTION   AND  RELIGIOUS   THOUGHT. 


oo^ 


ly  for  the  race  ?  Is  not  this  seeming  evil  also  a  real 
good  ? 

May  we  not,  then,  confldently  generalize  ?  May  we 
not  say  that  all  physical  evil  is  good  in  its  general  effect 
— that  every  law  of  Nature  is  beneficent  in  its  general 
operation,  and,  if  sometimes  evil  in  its  specific  operation, 
is  so  only  through  our  ignorance  ?  Partly  by  survival  of 
the  fittest,  and  partly  by  intelligence,  man,  like  other 
animals,  brings  himself  in  accord  with  the  laws  of  K'a- 
ture,  and  thus  appropriates  the  good  and  avoids  the  evil, 
and  Nature  becomes  beneficent  only.  But,  also  unlike 
any  other  animal,  man  by  rational  knowledge  makes  the 
laws  of  Nature  his  servants,  and  uses  them  for  his  own 
l^urposes,  thus  increasing  his  power  and  elevating  the 
plane  of  his  life. 

4.  Moral  Evil. — But  there  is  still  another  form  of 
evil,  the  most  dreadful  of  all.  This  one  may  be  called 
the  evil,  in  some  sense,  tlie  only  evil.  It  is  that  of  which 
all  other  forms  are  but  the  shadows  cast  backward  and 
downward  along  the  course  of  evolution  and  on  lower 
stages  of  existence.  This  consummation  of  all  evil  is 
sin  —  moral  disease  —  more  dreadfully  contagious  and 
deadly  than  any  organic  disease.  What  shall  we  say 
now  ?  Is  there  any  rational  explanation  of  this  evil  ? 
Is  there  any  possible  reason  or  excuse  for  an  all-wise,  all- 
powerful  Ruler  afflicting  man  alone  of  all  His  creatures 
with  this  greatest  of  all  evils  ?  In  all  other  cases,  the 
individual  and  the  ra€e  sacrifice  themselves  for  a  time 
physically  for  the  sake  of  final  spiritual  elevation  ;  but 


EVOLUTION   AND   THE   PROBLEM   OF  EVIL.    333 

this  is  spiiHtual  debasement.  In  all  other  cases,  there  is  a 
sacrifice  in  the  course  in  order  to  attain  the  goal,  but  this 
is  a  missing  of  the  goal  itself.  Is  there  any  view  which 
mitigates  this  evil,  any  philosophic  alchemy  which  can 
transmute  this  evil  into  good  ?  Age  after  age  the  human 
mind  has  prostrated  itself  in  helpless  paralysis  before 
this  problem.  Most  thinkers  have  been  content  to  say, 
*'Thou  hast  ordered  it  so.  Thou  art  good.  It  must  be 
right."  Bat  many,  and  among  them  some  of  the  best 
minds,  have  said,  '' Either  God  is  not  all-good,  or  else 
not  all-wise,  or  else  not  all-powerful,  or  else  there  is  no 
God  at  all."  Does  evolution  shed  any  light  on  this 
dread  problem  ?     I  believe  it  docs. 

We  have  said  that  all  other  evils  are  but  shadows  of 
this  one,  cast  backward  and  downward  on  earlier  stages 
of  CYolution  and  lower  forms  of  existence.  But  from 
the  evolution  point  of  view  these  earlier  and  lower  forms 
of  evil  are  rather  to  be  regarded  as /oreshado wings  of  the 
reality  to  come.  They  are  but  earlier  and  lower  stages 
of  the  evolution  of  the  same  tiling— emhrjonic  condi- 
tions of  the  now  full-grown  evil.  If  so,  then  the  same 
law  must  apply  here  also,  though,  as  we  shall  see,  with 
a  difference.  Here,  also,  the  individual  as  well  as  tlie 
race  finds  himself  surrounded  by  what  seems  an  evil  en- 
vironment, against  which  he  must  struggle.  The  spirit 
of  man  is  inclosed  and  conditioned  by  a  lower  environ- 
ment, which  he  must  subdue  or  perish.  Here,  then,  is 
again  a  deadly  conflict :  ^'a  law  in  the  members  warring 
against  the  law  of  the  siw.rit,  and  bringing  it  into  captiv- 


534       EVOLUTION   AND   KELIGIOUS   THOUGnT. 

ity  "  ;  a  law  of  selfism  warring  against  the  law  of  love,  and 
bringing  it  into  subjection ;  solicitations  to  debasement 
on  the  one  hand,  and  solicitations  to  wrong  others  on  the 
other.  How  shall  it  be  overcome  ?  What  is  the  reme- 
dy ?  Again  I  answer,  Knowledge  of  and  conformity  to 
the  laivs  of  the  moral  tuorlcl.  But,  as  in  other  cases,  so 
in  this  :  this  knowledge  of  and  conformity  to  law,  wdiich 
is  the  true  goal  of  humanity,  will  not  be  attained  unless 
it  is  forced  upon  us  by  necessity  and  in  self-defense — 
i.  e.,  by  evil. 

Now  supi^ose,  once  more,  this  knowledge  and  con- 
formity be  complete,  and  the  ideal  of  humanity  be  at- 
tained, and  from  this  final  and  highest  position  we  look 
back  over  the  whole  ground.  Shall  that  be  called  evil 
which  from  the  very  nature  of  a  moral  being  and  the 
laws  of  evolution  was  obviously  the  necessary  condition 
of  attaining  the  goal  ?  Shall  we  not  from  this  final  posi- 
tion call  it  a  good  in  disguise  ?  Evil,  doubtless,  it  seems 
to  us  who  suffer  and  stumble  and  mayhap  fall  by  the 
way  ;  but  shall  the  mishap  of  the  individual  be  weighed 
as  an  equivalent  against  the  evolution  of  the  race  and  the 
attainment  of  its  goal  ? 

Ah  !  there  is  the  rub.  It  is-  all  well  enough  to  talk 
of  sacrificing  the  physical  individual  to  the  race,  but 
not  so  the  spiritual.  If  we  believe  in  the  immortality  of 
the  human  spirit,  if  we  do  indeed  stand  related  to  God 
in  the  manner  explained  in  Chapter  IV,  then  moral 
evil  in  the  individual  has  an  entirely  peculiar  and  an 
eternal  significance — then  the  individual   human   spirit 


EVOLUTION  AND   THE  PROBLEM  OF  EVIL.    335 

has  an  infinite  worth  and  can  not  be  sacrificed  to  the 
race  ;  for  tiie  evohition  of  the  race  itself  is  only  in  order 
to  the  perfecting  of  individual  human  souls.  What 
shall  we  say  now  ?  I  answer  :  The  sacrifice  is  not  ne- 
cessary. There  is  in  the  realm  of  morals  alone  a  way  of 
escape — a  saving  element  which  redeems  the  individual 
without  violating  the  law.     Let  me  explain. 

It  will,  I  think,  be  admitted  by  all  that  innocence 
and  virtue  are  two  very  different  things.  Innocence  is 
a  pre-estahlislied,  virtue  a  self -established,  harmony  of 
spiritual  activities.  The  course  of  human  development, 
whether  individual  or  racial,  is  from  innocence  through 
more  or  less  discord  and  conflict  to  virtue.  And  virtue 
completed,  regarded  as  a  condition,  is  holiness,  as  an 
activity,  is  spiritual  freedom.  Not  happiness  nor  inno- 
cence but  virtue  is  the  goal  of  humanity.  Happiness 
will  surely  come  in  the  train  of  virtue,  but  if  we  seek 
primarily  happiness  we  miss  both.  Two  things  must  be 
borne  steadily  in  mind  :  virtue  is  the  goal  of  humanity  ; 
virtue  can  not  be  given,  it  must  be  self-acquired. 

Xow  we  have  already  seen  that  in  all  evil  the  remedy, 
which  not  only  cures  it  but  transmutes  it  into  good,  is 
knowledge  of  law  and  conformity  of  conduct  thereto — 
a  true  science  and  a  successful  art — in  a  word,  knowledge 
of  the  laws  of  God  and  obedience  to  these  laws.  In  the 
physical  world  ignorance  of  these  laws  is  necessarily  fatal, 
but  not  so  in  the  moral  world.  Ignorance  here  is  not 
necessarily  fatal  though  dangerous.  By  the  very  nature 
of  a  moral  being,  the  essential  thing  is  not  knowledge  but 


336       EVOLUTION   AND   RELIGIOUS  THOUGHT. 

character  or  virtue — the  loill  to  know  and  the  effort  to 
obe}^  In  the  ph3^sical  realm,  knowledge  is  the  goal ;  in 
the  moral  realm,  knowledge  is  only  in  order  to  virtue. 
Therefore,  in  the  case  of  the  individual  struggling  with 
moral  evil  within  and  without,  the  victory  is  always  in 
his  power.  If  he  fails,  it  is  his  own  fault.  His  utmost  ef- 
fort in  this  field  must  be  successful,  because  the  result  is 
not  external,  but  internal  and  in  the  realm  of  moral 
freedom.  The  spirit  of  man  is  self-acting  and  in  some 
sense,  though  not  absolutely,  self-existing,  and  can  not  be 
ruined  except  by  its  own  act.  In  the  moral  world,  where 
the  goal  is  not  knowledge  but  character,  attainment  must 
be  in  proportion  to  honest  endeavor  in  the  right  spirit. 

Evil,  then,  has  its  roots  in  the  necessary  law  of  evo- 
lution. It  is  a  necessary  condition  of  all  progress,  and 
pre-eminently  so  of  moral  j^rogress.  But  some  will  ask, 
*' Why  could  not  man  have  been  made  a  perfectly  pure, 
innocent,  happy  being,  unplagued  by  evil  and  incapable 
of  sin  ?  "  I  answer  :  The  thing  is  impossible  even  to 
omnipotence,  because  it  is  a  contradiction  in  terms. 
Such  a  being  would  also  be  incapable  of  virtue,  would 
not  be  a  moral  being  at  all,  would  not  in  fact  be  man. 
We  can  not  even  conceive  of  a  moral  being  without  free- 
dom to  choose.  We  can  not  even  conceive  of  virtue 
without  successful  conflict  with  solicitations  to  de- 
basement. But  these  solicitations  are  so  strong  and  so 
often  overcome  us,  that  we  are  prone  to  regard  the  solici- 
tations themselves  as  essential  evil  instead  of  our  weak 
surrender  to  them. 


EVOLUTION   AND  THE   PROBLEM  OF  EVIL.    337 

All  evolution,  all  j^rogress,  is  from  lower  to  higher 
plarie.  From  a  philosophic  point  of  view,  things  are  not 
good  and  evil,  but  only  higher  and  lower.  All  things  are 
good  in  their  true  places,  each  under  each,  and  all  must 
work  together  for  the  good  of  the  ideal  man.  Each 
lower  forms  the  basis  and  underlying  condition  of  the 
higher  ;  each  higher  must  subordinate  the  lower  to  its 
own  higher  uses,  or  else  it  fails  of  its  true  end.  The 
physical  world  forms  the  basis  and  condition  of  the  or- 
ganic, yet  the  organism  rises  to  a  higher  plane  only  by 
ceaseless  conflict  with  and  adaptation  to  the  physical  en- 
vironment, which  therefore  seems  in  some  sense  evil. 
The  organic  world  in  its  turn  underlies  and  conditions 
and  flourishes  the  rational  moral  world.  As  the  senses 
are  the  necessary  feeders  of  the  intellect,  so  the  appe- 
tites are  the  necessary  feeders  of  the  moral  nature. 
Yes,  even  the  lowest  sensual  appetites  are  the  necessary 
basis  and  nourishers  of  our  highest  moral  sentiments. 
And  yet  the  struggle  for  mastery  of  the  higher  spiritual 
with  the  lovver  animal  is  often  so  severe  that  the  latter 
seems  to  many  as  essential  evil  to  be  extirpated,  instead 
of  a  useful  servant  to  be  controlled.  This  view  is  asceti- 
cism. Now  the  whole  view  of  evil  usually  held  is  a  kind 
of  asceticism,  and  therefore,  like  asceticism,  must  be  only 
a  transition  phase  of  human  thought.  All  that  we  call 
evil  both  in  the  material  and  the  spiritual  world  is  good, 
so  long  as  we  hold  it  in  subjection  as  servants  to  the  spirit, 
and  only  becomes  evil  when  we  succumb.  All  evil  con- 
sists in  the  dominance  of  the  lower  over  the  higher;  all 


338      EV0LUTI05T  AND   KELIGIOUS  THOUGHT. 

goodwill  the  rational  use  of  the  lower  by  the  higher. 
True  virtue  consists,  not  in  the  extirpation  of  the  lower, 
but  in  its  subjection  to  the  higher.  The  stronger  the 
lower  is,  the  better,  if  only  it  be  held  in  subjection.  For 
the  hiojher  is  nourished  and  strenc^thened  bv  its  connec- 
tion  with  the  more  robust  lower,  and  the  lower  is  puri- 
fied, refined,  and  glorified  by  its  connection  with  tlie 
diviner  higher,  and  by  this  mutual  action  the  whole 
plane  of  being  is  elevated.  It  is  only  by  action  and  re- 
action of  all  parts  of  our  complex  nature  that  true  virtue 
is  attained. 


INDEX 


Acceleration,  law  of,  160. 
African  fauna  explained,  186. 
Agassiz,  his  greatest  result,  29,  43 ; 

relation  to  evolution,  32,  3Y,  43 ; 

relation  to  Darwin,  46  ;  compared 

with  Kepler,  47. 
Ages  of  geological  history,  1 6. 
Alpine  species  explained,  197. 
Amphibians,  development  of,  1S2. 
Analogy  and  homology,  81. 
Anima  of  animals,  295,  299. 
Animal  architecture,  styles  of,  91. 
Animal  kingdom,  primary  divisions 

of,  89. 
Animals,  relation  of  man  to,  293 ; 

spirit  embryonic  in,  293. 
Antiquity  of  man,  religion  and,  264  ; 

of  the  earth,  religion  and,  263. 
Aortic  arches,  proofs  of  evolution 

from,  133. 
Arthropods,  114. 
Artificial   production  of    varieties, 

204. 
Australia,  fauna  and  flora  of,  ex- 
plained, 182;  when  isolated,  184. 

Barriers  limit  faunal  and  floral  re- 
gions, 170. 


Beauty,  origin  of,  251. 

Birds'  tails,  changes  of,  156. 

Brain,vertebrate,  proofs  of  evolution 
from,  144 ;  vertebrate,  changes  of, 
in  phylogenic  series,  150;  relation 
to  mind,  304,  315. 

Brain-physiology  as  a  basis  for  ma- 
terialism, 288. 

Branching  tree  illustrates  evolu- 
tion, 13-15,  18,  92,  232. 

Brooks,  W.  K.,  on  the  cause  of  va- 
riations, 244. 

Californian  coast-islands,  fauna  and 
flora  of,  193. 

Causation,  idea  of,  from  within,  319. 

Centers  of  creation,  specific,  176. 

Cephalization,  153. 

Chambers,  his  views  on  evolution, 
34. 

Changes  slow  at  present,  248. 

Close-breeding,  effects  of,  218,  225. 

Coast-islands  of  California,  fauna 
and  flora  of,  193. 

Comparison,  method  of,  41. 

Conflict  between  religion  and  sci- 
ence, 262. 

Continental  faunas  and  floras,  170. 


340 


INDEX. 


Continental  island  life,  190. 

Continuity,  law  of,  53  ;  law  of,  ap- 
plied to  inorganic  forms,  54 ;  to 
organic  forms,  56, 

Cope's  law  of  acceleration,  160. 

Creation,  special,  30,  69;  specific 
centers  of,  176;  changes  in  our 
notions  of,  325. 

Cross-breeding,  law  of,  218. 

Cross-fertility  of  artificial  varieties, 
214. 

Cross-sterility,  77,  216. 

Cyclical  movement,  law  of,  16,  22. 

Darwin,  relation  to  Agassiz,  46 ; 
compared  with  Newton,  48  ;  fac- 
tors of  evolution  discovered  by, 
V4;  objections  to  his  theory  of 
evolution,  76. 

Derivation,  origin  of  inorganic  forms 
by,  54 ;  origin  of  organic  forms  by, 
56. 

Design,  idea  of,  from  within,  322  ; 
argument  from,  not  destroyed  by 
evolution,  323  ;  changes  in  our 
ideas  of,  325. 

Differentiation,  law  of,  11,  19;  law 
of,  in  embryonic  development,  19; 
law  of,  illustrated,  126;  of  the 
animal  kingdom  illustrated,  158. 

Disease,  necessity  of,  330. 

Divine  energy,  forms  of,  299. 

Divisions  of  the  animal  kingdom,  89. 

Dogmatism,  theological  and  scien- 
tific, 275. 

Domestication,  changes  produced  by, 
204. 

Egg,  development  of,  3,  19. 
Egyptian  species  unchanged  in  three 
thousand  years,  247. 


Embryology,    proofs    of    evolution 

from,  130. 
Environment,  physical,  73. 
Evil,  problem  of,  relation  of  evolu- 
tion to,   328 ;  physical,  necessity 
of,  329 ;  a  condition  of  progress 
329,   336;  organic,   necessity  of, 
330  ;  moral,  necessity  of,  332. 
Evolution,  what  is,  3,  8  ;  scope  of, 
3  ;  type  of,  3,  8  ;  examples  of,  5  ; 
popularly  limited  to  the  organic 
kingdom,   7;  progressive  change 
in,  9 ;  laws  of,  11;  illustrated  by 
branching   tree,    13-15,    IS,    92, 
232  ;  misconception  of,  14 ;  pro- 
duced   by    resident    forces,    27 ; 
germs  of  the  idea,  32 ;  relation  of 
Agassiz  to,  32,  37, 43  ;  Lamarck's 
views  on,  33  ;  Chambers's  views 
on,  34 ;  obstacle  to,  removed,  35  ; 
confliction     with    relidon   imar^i- 
nary,  45  ;  how  related  to  gravita- 
tion,  49 ;  general   evidences  of, 
53;  artificial,   60;  observed,  62; 
certainty   of,  65;  special   proofs 
of,  67  ;  factors  of,  73  ;  proofs  of, 
from  the  vertebrate  skeleton,  93 ; 
from  the  articulate  skeleton,  114  ; 
from  embryology,  130 ;  from  de- 
velopment  of   amphibians,    132; 
from   aortic   arches,    133;    from 
vertebrate  brain,  144  ;  from  rudi- 
raentary  organs,  161  ;  from  geo- 
graphical distribution  of   organ- 
isms, 165;  explains  geographical 
diversity,   177;  objection  to  this 
view,   199;  answer,   201;  proofs 
of,  from  artificial   modifications, 
204 ;  factors  of,  operative  in  do- 
mestication,     210  ;     paroxysmal, 


INDEX. 


341 


239;  material,  nearly  completed, 
249 ;  thoroudily  established,  257 ; 
relation  to  religion,  258,  264  ;  re- 
lation to  materialism,  266;  ne- 
cessitates great  change  in  relig- 
ious thought,  2Y7  ;  of  forces, 
297  ;  relation  to  revelation,  308  ; 
pantheistic  objection  answered, 
312  ;  relation  to  problem  of  evil, 
828. 
Experimental  method  largely  fails 
on  plane  of  life,  40. 

Factors  of  evolution,  73. 

Faculties,  evolution  of,  23. 

Faunas  and  floras,  geographical, 
165  ;  continental,  170  ;  marine, 
174 ;  special  cases  of  distinct, 
174;  of  Australia,  182;  of  Afri- 
ca, 186;  of  Madagascar,  187;  of 
continental  islands,  190;  of  the 
coast-islands  of  California,  1 93  ; 
of  oceanic  islands,  195;  of  lofty 
mountains,  197. 

Fish-tails,  changes  of,  in  develop- 
ment, 154  ;  in  evolution,  153. 

Fishes,  age  of,  17. 

Floras  and  faunas,  geographic  il, 
165. 

Force,  vital,  correlation  of,  36 ; 
planes  of,  296  ;  evolution  of,  297 ; 
idea  of,  from  within,  319. 

Forces,  resident,  evolution  by,  27  ; 
of  Nature  are  forms  of  Divine 
energy,  299. 

Fore-limbs,  vertebrate,  homologies 
of,  95. 

Generation,  spontaneous,  15. 
Geographical  faunas  and  floras,  165  ; 


diversity,  theory  of,  175  ;  diver- 
sity explained  by  evolution,  177  ; 
objection  to  this  view,  199;  an- 
swer, 201 ;  present  diversity  de- 
termined by  Glacial  epoch,  180. 

Geological  record,  imperfection  of, 
234. 

Glacial  epoch  determined  distribu- 
tion of  species,  177,  180,  197; 
changes  during,  in  America,  180 ; 
in  Europe,  181. 

God,  relation  of,  to  Nature,  279 ;  im- 
manence of,  in  Nature,  282  ;  rela- 
tion of,  to  man,  308  ;  personality 
of,  314  ;  necessary  belief  in,  326. 

Good  and  the  true,  relation  of,  259. 

Grasshopper,  external  anatomy  of, 
125. 

Gravitation,  relation  of,  to  evolu- 
tion, 49 ;  and  religion,  263. 

Gyroscope,  270. 

Heliocentric  theory  and  religion,  262. 
Hind-limbs,  vertebrate,  homologies 

of,  103. 
Horse,  genesis  of,  108. 
Homologies  of  vertebrate  skeleton, 

93  ;  of  vertebrate  fore-limbs,  95 ; 

of   vertebrate     hind-limbs,    103 ; 

of  articulate  skeleton,  114. 
Homology    and   analogy,    81  ;  only 

within  primary  divisions,  90. 
Hyatt,  A.,  on  Planorbis,  236. 

Idealism,  true  and  false,  283. 
Immortality  in  accord  with  law,  298. 
Individuality,    organic,  302  ;  spirit- 
ual, 302. 
Innocence    and    virtue    compared, 


342 


INDEX. 


Inorganic  forms,  law  of  continuity 
applied  to,  54. 

Intermediate  forms  between  arti- 
ficial varieties,  214. 

Islands,  continental  and  oceanic 
189. 

Kepler  compared  with  Agassiz,  47. 

Lamarck,  evolutionary  views  of,  33 
74. 

Law  of  differentiation,  11,  19  ;  of 
progress  of  the  whole,  13,  22  ;  of 
cyclical  movement,  16,  22;  of 
continuity,  o3  ;  of  continuity  ap- 
plied to  inorganic  forms,  54  ;  to 
organic  forms,  56  ;  of  differenti- 
ation illustrated,  126  ;  of  acceler- 
ation, 160  ;  of  cross-breeding,  218. 

Laws  of  evolution,  11,  19. 

Lepidosiren,  83. 

Life,  nature  of,  35 ;  imperfectly 
subject  to  experiment,  40;  rela- 
tion of,  to  philosophy,  259. 

Limbs,  vei'tebrate,  homology  of,  95. 

Links,  connecting,  12,  57,  127;  con- 
necting, elimination  of,  230  ;  con- 
necting, usually  absent  from  geo- 
logical faunas,  233. 

Liquidambar,  200,  202. 

Lobster,  external  anatomy  of,  118. 

Lungs,  formation  of,  82. 

MadagasCan  fauna  explained,  187. 

Mammals,  age  of,  17. 

Man,  age  of,  18  ;  relation  of,  to  Na- 
ture, 286  ;  relation  of,  to  animals, 
293 ;  spirit  of,  in  relation  to  the 
forces  of  Nature,  295,  29S  ;  rela- 
tion of  God  to,  308. 

Marsupials,  183. 


I  Materialism,    relation  of,  to   evolu- 
tion, 266  ;  basis  for,  in  brain-phys- 
j       iology,  288 ;  basis  for,  in   evolu- 
I      tion,  293. 
Methods,  scientific,  38. 
Migration  favors  diversification,  77. 
Mind,    relation    of,  to    brain,    304, 
315  ;  versus  mechanics  in  Nature, 
317. 
Mollusks,  age  of,  16. 
Monotremes,  183. 

Mystery,  changes  in  our  sense  of, 
324. 

Nature,  relation  of  God  to,  279  ;  im- 
manence of  God  in,  282 ;  relation 
of  man  to,  286 ;  has  no  meaning 
without  spirit,  306 ;  mind  versus 
mechanics  in,  317. 

Newton  compared  with  Darwin,  48. 

Nominalism  and  realism  reconciled, 
306. 

Obstacle  to  evolution  removed,  35. 
Oceanic  island  life,  195. 
Ontogenic  series,  9,  40. 
Or2:anic  forms,  views  of  origin  of, 

29,  68,  72,  274  ;  law  of  continuity 

applied  to,  56. 
Organs,  incipient,  252. 
Origin  of  varieties  unexplained,  252. 

Pantheism,    true    and    false,    284, 

312. 
Paroxysmal  evolution,  239. 
Personality  of  God,  314. 
Philosophy  and    life,  relations  of, 

259. 
Phylogenic  series,  10,  41. 
Planorbis  of  Steinheira,  236. 


INDEX. 


343 


Primal  animals,  12Y. 

Progress  of  the  whole,  law  of,  13, 

22. 
Progressive  change  in  evolution,  9. 

Ranges  of  organic  forms,  1G8. 

Realism  and  nominalism  reconciled, 
306. 

Record,  geological,  imperfection  of, 
234. 

ReUgion,  so-called  conflict  of,  with 
evolution,  45,  262. 

Religious  thought  to  be  reconstruct- 
ed, 277. 

Reproduction,  methods  of,  219. 

Reptiles,  age  of,  17. 

Revelation,  relation  of  evolution  to, 
308 ;  not  inconsistent  with  the 
laws  of  Nature,  309 ;  nature  of, 
310. 

Reversion  of  artificial  forms,  211. 

Romanes,  G.  J.,  his  idea  of  physio- 
logical selection,  76  ;  the  idea  ap- 
plied, 227. 

Rudimentary  organs,  proofs  of  evo- 
lution from,  161 ;  organs  in  man, 
163. 

Selection,  sexual,  74 ;  natural,  74, 
79 ;  physiological,  75,  79 ;  natu- 
ral, compared  with  artificial,  207  ; 
physiological,  applied,  227. 

Self-consciousness  the  sign  of  spirit- 
individuality,  3C2. 

Sequoia,  201,  202. 

Sexes,  characters  of,  compared, 
244. 

Shrimp,  external  anatomy  of,  116. 

Sin  a  condition  of  moral  evolution, 
332. 

16 


Skeleton,  vertebrate,  homologies  of, 
93  ;  articulate,  homologies  of, 
114;  articulate,  general  structure 
of,  116. 

Society,  progress  of,  25. 

Space  and  time  the  two  fundamental 
conditions  of  material  existence, 
48. 

Species,  natural,  more  permanent 
than  artificial  varieties,  211 ;  more 
distinct,  214;  cross-sterile,  214. 

Spirit  embryonic  in  animals,  293 ; 
of  man  related  to  anima  of  ani- 
mals, 295  ;  to  forces  of  Nature, 
295,  298 ;  no  meaning  in  Nature 
without,  306. 

Steinheim,  Planorbis  of,  236. 

Taxonomic  series,  9,  40. 

Temperature-regions,  166. 

Tread,  plantigrade  and  digitigrade, 

105. 
True    and    the    good,   relation  of, 

259. 
Truth  tested  by  effect  on  life,  259 ; 

not  compromise,  273. 
Types,  generalized,  13. 

Use  and  disuse  of  organs,  73. 
Useless  structures,  how  produced, 

76. 

Variation  depends  on  sexual  repro- 
duction, 220;  caused  by  unfavor- 
able conditions,  246. 

Varieties,  artificial  production  of, 
204,  217;  artificial  production  of, 
illustrated,  206  ;  natural  and  arti- 
ficial, compared,  210;  origin  of, 
unexplained,  252. 


su 


INDEX. 


"Vestiges  of  Creation,"  34. 
Virtue   and    innocence    compared, 

335. 
Vital  principle,  305. 


Voluntary  social  progress,  26. 

Whales,    rudimentary    organs    of, 
162. 


THE   EXD. 


A   LIBRARY 

OF    THE    MOST     IMPORTANT 

STANDARD  WORKS  ON  EVOLUTION. 


I. 

Origin  of  Species  by  Means  of  Natural  Selection,  or  the  Preser- 
vation  of  Favored  Races  in  the  Struggle  for  Life.  By  Charles  Dar- 
win, LL.  D.,  F.  R.  S.  New  and  revised  edition,  with  Additions. 
12mo.     Cloth,  $2.00. 

"Personally  and  practically  exercised  in  zoology,  in  minute  anatomy,  in 
geology,  a  student  of  geographical  distribution,  not  in  maps  and  in  mu- 
seums, but  by  long  voyages  and  laborious  collection ;  having  largely  ad- 
vanced each  of  these  branches  of  science,  and  having  spent  many  years  in 
gathering  and  sifting  materials  for  his  present  work,_  the  store  of  accurately- 
registered  facts  upon  which  the  author  of  the  '  Oripn  of  Species '  is  able  to 
draw  at  will  is  prodigious." — Professor  T.  H.  Huxley. 

II. 

Variation  of  Animals  and  Plants  under  Domestication.    By 

Charles  Darwin,  LL.  D.,  F.  R.  S.     With  Illustrations.     Revised  edi- 
tion.    2  vols.,  12mo.     Cloth,  $5.00. 

"  We  shall  learn  something  of  the  laws  of  inheritance,  of  the  effects  of 
crossing  different  breeds,  and  on  that  sterility  which  often  supervenes  when 
organic  beings  are  removed  from  their  natural  conditions  of  life,  and  like- 
wise when  they  are  too  closely  interbred." — From  the  Introduction. 

III. 

Descent  of  Man,  and  Selection  in  Relation  to  SeXo  By  Charles 
Darwin,  LL.  D.,  F.  R.  S.  With  many  Illustrations.  A  new  edition. 
Timo.     Cloth,  $3.00. 

"  In  these  volumes  Mr.  Darwin  has  brought  forward  all  the  facts  and 
arguments  which  science  has  to  offer  in  favor  of  the  doctrine  that  man  has 
arisen  by  gradual  development  from  the  lowest  point  of  animal  life.  Aside 
from  the  logical  purpose  which  Mr.  Darwin  had  in  view,  his  work  is  an 
original  and  fascinating  contribution  to  the  most  interesting  portion  of  nat- 
ural Mstory." 

IV. 

On  the  Origin  of  Species  ;  or.  The  Causes  of  the  Phenomena  of  Or- 
ganic Nature.  By  Professor  T.  H.  Huxley,  F.  R.  S.  12mo.  Cloth,  $1.00. 

"  Those  who  disencumber  Darwinism  of  its  difficulties,  simplify  its  state- 
ments, relieve  it  of  technicalities,  and  bring  it  so  distinctly  within  the  hori- 
zon of  ordinary  apprehension  that  persons  of  common  sense  may  judge  for 
themselves,  perform  an  invaluable  service.  Such  is  the  character  of  the 
present  volume." — From  the  Preface  to  the  American  edition. 

V. 

Darwiniana.  Essays  and  Reviews  pertainin*:  to  Darwinism.  By  Asa 
Gray,  Fisher  Professor  of  Natural  History  (Botany)  in  Harvard  Uni- 
versity.    12mo.     Cloth,  $2.00. 

"  Although  Professor  Gray  is  widely  known  in  the  world  of  science  for 
his  botanical  researches,  but  few  are  aware  that  he  is  a  pronounced  and  ua- 


A  STANDARD  F VOLUTION  LIBRARY. 

flinching  Darwinian.  His  contributions  to  the  discussion  are  varied  and 
valuable,  and  as  collected  in  the  present  volume  thev  will  be  seen  to  estab- 
lish a  claim  upon  the  thinking  world,  which  will  be  extensively  felt  and 
cordially  acknowledged.  These  papers  not  only  illustrate  the  'historj'  of 
the  controversy,  and  the  progress  of  the  discussion,  but  they  form  perliaps 
the  fullest  and  most  trustworthy  exposition  of  what  is  to  be  properly  under- 
stood by  '  Darwinism '  that  is  to  be  tbund  in  our  language.  To  all  those 
timid  souls  who  are  worried  about  the  progress  of  science,  and  the  danger 
that  it  will  subvert  the  foundations  of  their  faith,  we  recommend  the  dis- 
passionate perusal  of  this  volume." — The  Popular  Science  Monthly. 

VI. 
Heredity :  A  Psychological  Study  of  its  Phenomena,  Laws,  Causes,  and 
Consequences.    From  the  French  of  Th.  Ribot.    12mo.    Cloth,  $2.00. 

"  Heredity  is  that  biological  law  by  which  all  beings  endowed  with  life 
tend  to  repeat  themselves  in  their  descendants  :  it  is  for  the  species  what 
personal  identity  is  for  the  individual.  The  physiological  side  ofthis  subject 
has  been  diligently  studied,  but  not  so  its  psychol(^ical  side.  We  propose 
to  supply  this  deficiency  in   the  present  work." — From  the  Introduction. 

VII. 

Hereditary  Genius:  An  Inquiry  into  its  Laws  and  Consequences. 
By  Francis  Galton,  F.  R.  S.,  etc.  New  and  revised  edition,  with  an 
American  Preface.      12mo.     Cloth,  $2.00. 

"  The  following  pages  embody  the  result  of  the  fii-st  vigorous  and  me- 
thodical effort  to  treat  the  question  in  the  true  scientific  spirit,  and  place 
it  upon  the  proper  inductive  basis.  Mr.  Galton  proves,  by  overwhelming 
evidence,  that  genius,  talent,  or  whatever  we  term  great  mental  capacity, 
follows  the  law  of  organic  transmission — runs  in  families,  and  is  an  affair  "or 
blood  and  breed  ;  and  that  a  sphere  of  phenomena  hitherto  deemed  capri- 
cious and  defiant  of  rule  is,  nevertheless,  within  the  operation  of  ascertain- 
able law." — From  the  American  Preface. 

VIII. 
The  Eyolution  of  Man.      A  Popular  Exposition  of  the  Principal 
Points  of  Human  Ontogeny  and  Phylogeny.     From  the  German  of 
Ernst  Haeckel,  Professor  in  the  University  of  Jena.     With  nmnef^- 
ous  Illustrations.     2  vols.,  12mo.     Cloth,  $5.00. 

"In  this  excellent  translation  of  Professor  Haeckel's  work,  the  English 
reader  has  access  to  the  latest  doctrines  of  the  Continental  school  of  evolu- 
tion, in  its  application  to  the  history  of  man." 

IX. 

The  History  of  Creation  ;  or,  the  Development  of  the  Earth  and  its 
Inhabitants  by  the  Action  of  Natural  Causes.  A  Popular  Exposition 
of  the  Doctrine  of  Evolution  in  General,  and  of  that  of  Darwin,  Goe- 
the, and  Lamarck  in  Particular.  By  Ernst  Haeckel,  Professor  in 
the  University  of  Jena.  The  translation  revised  by  Professor  E.  Ray 
Lankester.  Illustrated  with  Lithographic  Plates.  2  vols.,  12mo. 
Cloth,  15.00. 

"  The  book  has  been  translated  into  several  languages.  I  hope  that  it 
may  also  find  sympathy  in  the  fatherland  of  Darwin,  the  more  so  since  it 
contains  special  morphological  evidence  in  favor  of  many  of  the  most  impor- 
tant doctrines  with  whichthis  greatest  naturalist  of  our  century  has  emiched 
•eience." — From  the  Preface. 


A   STANDARD  EVOLUTION  LIBRARY. 


X. 
Heligion  and  ScieneP=     A  Series  of  Sunday  Lectures  on  the  Rlatione 
of  Natural  and  Hevep-led  Religion,  or  the  Truths  revealed  in  Nature 
and  Scripture.     By  Joseph  Le  Conte,  LL.  D.     12mo.     Cloth,  $1.50. 

XI. 

Prehistoric  Times,  as  illustrated  by  Ancient  Remains  and 
tlie  Manners  and  Customs  of  Modern  Savages.  By  Sir  JohxV 
Lubbock,  Bart.  Illustrated.  Entirely  new  revised  edition.  8va 
Cloth,  $5.00. 

The  book  ranks  among  the  noblest  -works  of  the  interesting  and  impor- 
tant class  to  which  it  belongs.  As  a  resume  of  our  present  knowledge  of 
prehistoric  man,  it  leaves  nothing  to  be  desired.  It  ia  not  only  a  good  book 
of  reference,  but  the  best  on  the  subject. 

XII. 
Winners  in  Life's  Race  ;  or,  The  Great  Backboned  Family.    By  Ara- 
BELLA  B.  Buckley,  author  of   "  The  Fairy-Land  of   Science "  and 
"  Life  and  her  Children."      With   numerous   Illustrations.      12mo. 
Cloth,  gilt  side  and  back,  $1.50. 

XIII, 
Physics  and  Politics ;  or,  Thoughts  on  the  Application  of  the  Priu' 
ciples  of  "Natural  Selection"  and  "  Inheritance  "  to  Political  Society. 
By  Walter  Bagehot.     12mo.     Cloth,  $1.50. 

XIV. 

The  Theory  of  Descent  and  Darwinism.  By  Professor  Oscar 
Schmidt.     With  26  Woodcuts.     12mo.     $1.50. 

"  The  facts  upon  which  tlie  Darwinian  theory  is  based  are  presented  in 
an  effective  manner,  conclusions  are  ably  defended,  and  the  question  is 
treated  in  more  compact  and  available  style  than  in  any  other  work  on  the 
same  topic  that  has  yet  appeared.  It  is  a  valuable  addition  to  the  '  Interna- 
tional Scientific  Series.'  " — Boston  Post. 

XV. 

Outline  of  the  Evolution  Philosophy.  By  Dr.  M.  E.  Gazelles. 
Translated  from  the  French,  by  the  Rev.  0.  B.  Frothingham  ;  with  an 
Appendix,  by  E.  L.  Youmans,  M.  D.     12mo.     Cloth,  $1.00. 

'  "  This  unpretentious  little  work  will,  no  doubt,  be  used  by  thousands  to 
whom  the  publications  of  Mr.  Herbert  Spencer  are  inaccessible  and  those  of 
Auguste  Comte  repellent,  by  reason  of  their  prolLxity  and  vagueness.  In  a 
short  space  Dr.  Gazelles  has  managed  to  compress  the  whole  outline  and 
scope  of  Mr.  Spencer's  system,  with  his  views  of  the  doctrine  of  progress 
and  law  of  evolution,  and  a  clear  view  of  the  principles  of  positivism." — 
JVaiure  (London). 

XVI. 

Principles  of  Geolo^ry ;  or.  The  Modern  Changes  of  the  Earth  and 
its  Inhabitants,  considered  as  illustrative  of  Geology.  By  Sir  Charles 
Lyell,  Bart.  Illustrated  with  Maps,  Plates,  and  Woodcuts.  A  new 
and  entirely  revised  edition.     2  vols.     Royal  8vo.     Cloth,  $8.00. 

The  "  Principles  of  Geology"  may  be  looked  upon  with  pride,  not  only 
as  a  representative  of  English  science,  but  as  without  a  rival  or  its  kincl 
anywhere.     Growing  in  fullness  and  accuracy  with  the  growth  of  experi- 


A   STANDARD  EVOLUTION  LIBRARY. 


ence  and  observation  in  every  region  of  the  world,  the  work  has  incorporated 
with  itself  each  established  discovery,  and  has  been  modified  by  every  hy- 
pothesis of  value  which  has  been  brought  to  bear  upon,  or  been  evolved 
from,  the  most  recent  body  of  facts. 

XVII. 

Elements  of  Geology.  A  Text-Book  for  Colleges  and  for  the  General 
Reader.  By  Joseph  Lb  Conte,  LL.  D.,  Professor  of  Geology  and 
Natural  History  in  the  University  of  California.  Revised  and  en- 
larged edition.   12mo.  With  upward  of  900  Illustrations.  Cloth,  $4.00. 

XVIII. 

Animal  Life,  as  afiFected  by  the  Natural  Conditions  of  Exist- 
ence. By  Karl  Semper,  Professor  of  the  University  of  Wiirzburg. 
With  Maps  and  100  Woodcuts.     12mo.     Cloth,  $2.00., 

XIX. 
Crayflsll :  An  Introduction  to  the  Study  of  Zoology.    By  Professor  T.  H, 
Huxley,  F.  R.  S.     With  82  Illustrations.     12mo.     Cloth,  $1.75. 

XX. 

Anthropology :  An  Introduction  to  the  Study  of  Man  and  Civilization. 
By  Edward  B.  Tylor,  F.  R.  S.    With  78  Illustrations.    12mo.    Cloth, 

$2.00. 

*'  The  students  who  read  Mr.  Tylor's  book  may  congratulate  themselves 
upon  having  obtained  so  easy,  pleasant,  and  wortman-like  an  introduction 
to  a  fascinating  and  dehghtfiil  science." — London  Athenaeum. 

XXI. 
First  Principles.     Bv  Herbert  Spencer.     Part  I.  The  Unknowable. 
Part  II.  The  Knowable.     1  vol.,  12mo.     $2.00. 

XXII. 
The  Principles  of  Biology.     By  Herbert  Spencer.     2  vols.,  12mo. 
$4.00. 

xxni. 
The  Principles  of  Psychology.      By   Herbert  Spencer.     2  vols., 

12mo.     $4.00. 

XXIV. 

The   Principles   of  Sociology.       By    Herbert    Spencer.       12mo. 

2  vols.     $4.00. 

XXV. 

The  Data  of  Ethics.  Bv  Herbert  Spencer.  Being  Part  I,  Vol.  I, 
of  "  The  Principles  of  Morality."     12mo.     Cloth,  $1.25. 

XXVI. 

Illustrations  of  Universal  Progress.  By  Herbert  Spencer, 
12mo.     Cloth,  $2.00. 


For  sale  hy  all  hooksellers  ;  or,  sent  by  mail,  post-paid,  on  receipt  of  price. 


New  York:  D.  APPLETON  &  CO.,  1,  3,  &  5  Bond  Street. 


D,  APPLETON  &  CO.'S  PUBLICATIONS. 

THE  HUMAN  SPECIES.  By  A.  De  Quatrefages,  Trofessor  of 
Anthropology  in  the  Museum  of  Natural  History,  Paris.  12mo. 
Cloth,  $2.00. 

The  work  tre;its  of  the  unity,  origin,  antiquity,  and  orij^inal  localization  of  the 
human  species,  peopling  of  the  globe,  acclimatization,  primitive  man,  formation  of  the 
human  races,  fossil  human  races,  present  human  races,  and  the  physical  and  psycho- 
logical characters  of  mankind. 

STUDENT'S  TEXT-BOOK  OF  COLOR;  or,  MODERN 
CHROMATICS.  With  Applications  to  Art  and  Industry.  With 
130  Original  Illustrations,  and  Frontispiece  in  Colors.  By  Ogde.v 
N.  Rood,  Professor  of  Physics  in  Columbia  College.     12rao.     Cloth. 

$2.00. 

"  In  this  interesting  book  Professor  Eood,  who  as  a  distinguished  Professor  of 
Physics  in  Columbia  College,  United  States,  must  be  accepted  as  a  competent  authority 
on  the  bi-anch  of  science  of  which  he  treats,  deals  briefly  and  succinctly  with  what 
may  be  termed  the  scientific  rationale  of  his  subject.  But  the  chief  value  of  his  work 
is  to  be  attributed  to  the  fact  that  he  is  himself  an  accomplished  artist  as  well  as  an  au- 
thoritative expounder  of  science." — Edinburgh  Bevieiv,  October,  1879,  m  an  article 
on  "  The  Philosophy  of  Color. ''^ 

EDUCATION    AS    A   SCIENCE.     By  Alexander  Bain,  LL.  D. 

12mo.     Cloth,  $1.75. 

"This  work  must  be  pronounced  the  most  remarkable  discussion  of  educational 
problems  which  has  been  published  in  our  day.  We  do  not  hesitate  to  bespeak  for  it 
the  widest  circulation  and  the  most  earnest  attention.  It  should  be  in  the  hands  of 
every  school-teacher  and  friend  of  education  throughout  the  laud." — A^eiv  York  Sun. 

A  HISTORY  OF  THE  GROWTH  OF  THE  STEAM- 
ENGINE.  By  Robert  H.  Thurston,  A.  M.,  C.  E.,  Professor  of 
Mechanical  Engineering  in  the  Stevens  Institute  of  Technology, 
Hoboken,  N.  J.,  etc.  With  163  Illustrations,  including  15  Portraits. 
12mo.     Cloth,  $2.50. 

"  Professor  Thurston  almost  exhausts  his  subject ;  details  of  mechanism  are  followed 
by  interesting  biographies  of  the  more  important  inventors.  If,  as  is  contended,  the 
eteam-engine  is  the  most  important  physical  agent  in  civilizing  the  world,  its  history 
is  a  desideratum,  and  the  readers  of  the  present  work  will  agree  that  it  could  have  a 
no  more  amusing  and  intelligent  historian  than  our  author." — Boston  Gazette. 

STUDIES  IN  SPECTRUM  ANALYSIS.  By  J.  Xorman  Lock- 
YER,  F.  R.  S.,  Correspondent  of  the  Institute  of  France,  etc.  With 
60  Illustrations.     12mo.     Cloth,  $2.50. 

"The  study  of  spectrum  analysis  is  one  fraught  with  a  peculiar  fascination,  and 
Bome  of  the  author's  experiments  are  exceedingly  picturesque  in  their  results.  They 
are  so  lucidly  described,  too,  that  the  reader  keeps  on,  from  page  to  page,  never 
flagging  in  interest  in  the  matter  before  him,  nor  putting  down  the  book  until  the  last 
page  is  reached.'"— xVezi;  York  Evening  Exin-ess. 


New  York ;   D.  APPLETON  &  CO.,  1,  3,  &  5  Bond  Street. 


D,  APPLETON  &  CO/S  PUBLICATIONS. 


GENERAL  PHYSIOLOGY  OF  MUSCLES  AND  NERVES. 

By  Dr.  I.  Rosenthal,  Professor  of  Physiology  at  the  University  of 
Erlangen.  With  seventy-five  Woodcuts.  ("International  Scientific 
Series.")     12mo.     Cloth,  $1.50. 

"  The  attempt  at  a  connected  account  of  the  general  phyeiology  of  muscles  anri 
nerves  is,  as  far  as  I  know,  the  first  of  its  kind.  The  general  data  for  this  branch 
of  science  have  been  gained  only  within  the  past  thirty  yeais.'"'— Extract  from 
Preface. 

SIGHT  :  An  Exposition  of  the  Principles  of  Monocular  and  Binocular 
Vision.  By  Joseph  Le  Conte,  LL.  D.,  author  of  "Elements  of  Ge- 
ology " ;  "  Religion  and  Science  " ;  and  Professor  of  Geology  and 
Natural  History  in  the  University  of  California.  With  numerous 
Illustrations.    12mo.    Cloth,  $1.50. 

"  It  is  pleasant  to  find  an  American  book  which  can  rank  with  the  very  best 
of  foreign  works  on  this  subject.  Professor  Le  Conte  iias  long  been  known  as 
an  original  investigator  in  tbis  department ;  all  that  he  gives  us  is  treated  with 
a  master-hand."— r/ie  Nation. 

ANIMAL  LIFE,  as  affected  by  the  Natural  Conditions  of  Existence. 
By  Karl  Semper,  Professor  of  the  University  of  Wiirzburg.  With 
2  Maps  and  106  Woodcuts,  and  Index.     12mo.    Cloth,  $2.00. 

"Tliis  is  in  many  respects  one  of  the  most  interesting  contributions  to 
zoological  literature  which  has  appeared  for  some  iivaQ.''— Nature. 

THE  ATOMIC  THEORY.  By  Ad.  Wurtz,  Membre  de  I'Institut; 
Doyen  Honoraire  de  la  Faculte  de  Medecine  ;  Professeur  h.  la  Faculte 
des  Sciences  de  Paris.  Translated  by  E.  Clemixshaw,  M.  A.,  F.  C. 
S.,  F.  I.  C,  Assistant  Master  at  Sherborne  School.  12mo.  Cloth, 
$1.50. 

"  There  was  need  for  a  book  like  this,  which  discusses  the  atomic  theory  both 
in  its  historic  evolution  and  in  its  present  form.  And  perhaps  no  man  of  this 
age  could  have  been  selected  so  able  to  perform  the  task  in  a  masterly  way  as 
the  illustrious  French  chemist.  Adolph  Wurtz.  It  is  impossible  to  convey  to  the 
reader,  in  a  notice  like  this,  any  adequate  idea  of  the  scope,  lucid  instructiveness, 
and  scientific  interest  of  Professor  Wurtz's  book.  The  modern  problems  of 
chemistry,  which  are  commonly  so  obscure  from  imperfect  exposition,  are  here 
made  wonderfully  clear  and  attractive." — Tfie  Popular  Science  Monthly. 

THE  CRAYFISH.  An  Introduction  to  the  Study  of  Zoology.  By 
Professor  T.  H.  Huxley,  F.R.  S.  With  82  Illustrations.  12mo. 
Cloth,  $1.'75. 

"Whoever  will  follow  these  pages,  crayfish  in  hand,  and  will  try  to  verify  for 
himself  the  statements  which  they  contain,  will  find  himself  brous-ht  face  to  face 
with  all  the  great  zoological  questions  which  excite  so  lively  an  interest  at  the 
present  day." 

"The  reader  of  this  valuable  monograph  will  lay  it  down  with  a  feeling  of 
wonder  at  the  amount  and  variety  of  matter  which  has  been  got  out  of  so  seem- 
ingly slight  and  unpretending  a  subject." — Saturday  Eeview. 


New  York:   D.  APPLETOX  &   CO.,  1,  3,  cfe  5  Bond  Street. 


D.  APPLETON  &  CO/S  PUBLICATIONS. 


SUICIDE :  An  Essay  in  Comparative  Moral  Statistics.  By  Henrt 
MoRSKLLi,  Professor  of  Psychological  Medicine  in  the  Royal  Univer- 
sity, Turin.     12mo.     Cloth,  $1.75. 

"  Suicide  "  is  a  scientific  inquiry,  on  the  basis  of  the  statistical  method,  into  the  laws 
of  suicidal  phenomena.  Dealing  with  the  subject  as  a  branch  of  social  science,  it  con- 
siders the  increase  of  suicide  in  different  countries,  and  the  comparison  of  nations, 
races,  and  periods  in  its  manifestation.  The  influences  of  aiie,  sex,  constitution,  cli- 
mate, season,  occupation,  religion,  prevailing  ideas,  the  elements  of  character,  and  the 
tendencies  of  civilization,  are  comprehensively  analyzed  in  their  bearing  upon  the  pro- 
pensity to  self-destruction.  Professor  Morselli  is  an  eminent  European  authority  on 
this  subject.  It  is  accompanied  by  colored  map.s  illustrating  pictorially  the  results  of 
statistical  inquiries. 

VOLCANOES:   What  they  Are  and  what  they  Teach.     By 

J.  W.  JuDD,  Professor  of  Geology  in  the  Royal  School  of  Mines 

(London).     With  Ninety-six  Illustrations.     12mo.     Cloth,  $2.00. 

"  In  no  field  has  modern  research  been  more  fruitful  than  in  that  of  which  Professor 
Judd  gives  a  popular  account  in  the  present  volume.  The  great  lines  of  dynamical, 
geological,  and  meteorological  inquiry  converge  upon  the  grand  problem  of  the  interior 
constitution  of  the  earth,  and  the  vast  influence  of  subterranean  agencies.  .  .  .  His 
book  is  very  far  from  being  a  mere  dry  description  of  volcanoes  and  their  eruptions;  it 
is  rather  a  presentation  of  the  terrestrial  facts  and  laws  with  which  volcanic  phenomena 
are  associated."' — Popular  Science  Monthly. 

THE  SUN.  By  C.  A.  Young,  Ph.  D.,  LL.  B.,  Professor  of  Astronomy 
in  the  College  of  New  Jersey.  With  numerous  Illustrations. 
Third  edition,  revised,  with  Supplementary  Note.     12mo.     Cloth, 

$2.00. 

The  "  Supplementary  Note"  gives  important  developments  in  solar  astronomy 
since  the  publication  of  the  second  edition  in  1882. 

"  It  would  take  a  cyclopaedia  to  represent  all  that  has  been  done  toward  clearing  up 
the  solar  mysteries.  Professor  Young  has  summarized  the  information,  and  presented 
it  in  a  form  completely  available  for  general  readers.  There  is  no  rhetoric  in  his 
book;  he  trusts  the  grandeur  of  his  theme  to  kindle  interest  and  impress  the  feelings. 
His  statements  are  plain,  direct,  clear,  and  condensed,  though  ample  enough  for  his 
purpose,  and  the  substance  of  what  is  generally  wanted  will  be  found  accurately  given 
in  his  pages.' — Popular  Science  Monthly. 

ILLUSIONS :  A  Psychological  Study.     By  James  Sully,  author 
of  "  Sensation  and  Intuition,"  etc.     12mo.     Cloth,  $1.50. 

This  volume  takes  a  wide  survey  of  the  field  of  error  embracing  in  its  view  not  only 
the  illusions  commonly  regarded  as  of  the  nature  of  mental  aberrations  or  hallucina- 
tions, but  also  other  illusions  arising  from  that  capacity  for  error  which  belongs  essen- 
tially to  rational  human  nature.  The  author  has  endeavored  to  keep  to  a  strictly 
scientific  treatment— that  is  to  say,  the  description  and  classification  of  acknowledged 
errors,  and  the  exposition  of  them  by  a  reference  to  their  psychical  and  physical  con- 
ditions. 

"  This  is  not  a  technical  work,  but  one  of  wide  popular  interest,  in  the  principles 
and  results  of  which  every  one  is  concerned.  The  illusions  of  i)ercei)tion  of  the  senses 
and  of  dreams  are  first  considered,  and  then  the  author  passes  to  the  illusions  of  in- 
trospection, errors  of  insight,  illusions  of  memory,  and  illusions  of  belief.  The  work 
is  a  noteworthy  contribution  to  the  original  progress  of  thought,  and  may  be  relied 
upon  as  representing  the  present  state  of  knowledge  on  the  important  subject  to 
which  it  is  devoted."— Pp^Jw/ar  Science  Monthly. 


New  York:   D.  APPLETON  &  CO.,  1,  3,  &  5  Bond  Street. 


D.  APPLETON  d  CO, '8  PUBLICATIONS. 

THE   BRAIN  AXD  ITS   FUJfCTIONS.     By  J.  Luts,  Physician 

to   the    Hospice   de    la   Salpetriere.      With   Illustrations.      12mo. 

Cloth,  $1.50. 

"No  livlBg  physiolopfist  is  better  entitled  to  speak  with  authority  upon  the 
structure  and  functions  of  the  brain  than  Dr.  Luys.  His  studies  on  the  anatomy 
of  the  nervous  system  are  aclj;nowledged  to  be  the  fullest  and  most  systematic 
ever  undertaken.  Dr.  Luys  supports  his  conclusions  not  only  by  hie  own  ana- 
tomical researches,  but  also  by  many  functional  observations  of  various  other 
physiologists,  includincj  of  course  Professor  Ferrier's  now  classical  experi- 
me'nts."— >Si.  James's  Gazette. 

"Dr.  Luys,  at  the  head  of  the  great  French  Insane  Asyhim,  is  one  of  the  most 
eminent  and  successful  investigators  of  cerebral  science  now  living  ;  and  he  has 
given  unquestionably  the  clearest  and  mo?t  interesting  brief  account  yet  made 
of  the  structure  and  operations  of  the  brain.  We  have  been  fascinated  by  this 
volume  more  than  by  any  other  treatise  we  have  yet  seen  on  the  machinery  of 
sensibility  and  thought;  and  we  have  been  instructed  not  only  by  much  that  is 
new,  but  by  many  sagacious  practical  hints  such  as  it  is  well  for  everybody  to 
understand."— TAe  Popular  Science  Monthly. 

THE      CONCEPTS      AND      THEORIES      OF      MODERN 

PHYSICS.     By  J.  B.  Stallo.     12mo.     Cloth,  $1.75. 

"Judge  Stallo's  work  is  an  inquiry  into  the  validity  of  those  mechanical  con- 
ceptions of  the  universe  which  are  now  held  as  fundamental  in  physical  science. 
He  takes  up  the  leading  modern  doctrines  which  are  based  upon  this  mechanical 
conception,  such  as  the  atomic  constitution  of  matter,  the  kinetic  theory  of  gases, 
the  conservation  of  energy,  the  neDular  hypothesis,  and  other  views,  to  find  how 
much  stands  upon  solid  empirical  ground,  and  how  much  rests  upon  metaphys- 
ical speculation.  Since  the  ajjpearance  of  Dr.  Draper's  '  Religion  and  Science,' 
no  book  has  been  published  in  the  country  calculated  to  make  so  deep  an  im- 
pression on  thoughtful  and  educated  readers  as  this  volume.  .  .  .  The  range 
and  minuteness  of  the  author's  learning,  the  acuteness  of  his  reasoning,  and  the 
singular  precision  and  clearness  of  his  style,  are  qualities  which  very  seldom 
have  been  jointly  exhibited  in  a  scientific  treatise."— ^Vei^  York  Sun. 

THE  FORMATION  OF  VEGETABLE  MOULD,  through 
the  Action  of  Worms,  with  Observations  on  their 
Habits.  By  Charles  Darwin,  LL.  D.,  F.  R.  S.,  author  of  "  On 
the  Origin  of  Species,"  etc.,  etc.  With  Illustrations.  12mo. 
Cloth,  $1.50. 

"  Mr.  Darwin's  little  volume  on  the  habits  and  instincts  of  earth-worms  is  no 
less  marked  than  the  earlier  or  more  elaborate  efl'orts  of  his  genius  by  freshness 
of  observation,  unfailing  power  of  interpreting  and  correlating  facte,  and  logical 
vigor  in  generalizing  upon  them.  The  main  purpose  of  the  work  is  to  point  out 
the  share  which  worms  have  taken  in  the  formation  of  the  layer  of  vegetable 
mould  which  covers  the  whole  surface  of  the  land  in  every  moderately  humid 
country.  All  lovers  of  nature  will  unite  in  thanking  Mr.  Darwin  for  the  new  and 
interesting  light  he  has  thrown  upon  a  subject  so  long  overlooked,  yet  so  full  of 
interest  and  mstruction,  as  the  structure  and  the  labors  of  the  earth-worm.'' — 
Saturday  Review. 

"  Respecting  worms  as  among  the  most  useful  portions  of  animate  nature. 
Dr.  Darwin  relates,  in  this  remarkable  book,  their  structure  and  habits,  the 
part  they  have  played  in  the  burial  of  ancient  buildings  and  the  denudation  of 
the  land,  in  the  disintegraticm  of  rocks,  the  preparation  of  soil  for  the  growth 
of  plants,  and  in  the  natural  history  of  the  world." — Boston  Advertiser. 

New  York :  D.  APPLETON  &  CO.,  1,  3,  &  6  Bond  Street. 


D.  APPLETON  &  00/S  PUBLICATIONS. 

A.NTS,  BEES,  AND  WASPS.  A  Record  of  Observations  on  the 
Habits  of  the  Social  Hymenoptera.  By  Sir  John  Lubbock,  Bart., 
M.  P.,  F.  R.  S.,  etc.,  author  of  "  Origin  of  Civilization,  and  the  Primi- 
tive Condition  of  Man,"  etc.,  etc.  With  Colored  Plates.  12ino. 
Cloth,  §2.00. 

"  This  volume  contains  the  record  of  various  experiments  made  with  ants,  bees,  and 
wasps  during  the  last  ten  years,  with  a  view  to  test  their  mental  condition  and  powers 
of  sense.  The  principal  point  in  which  Sir  John's  mode  of  experiment  differs  'rom 
those  of  Huber,  Forel,  McCook,  and  others,  is  that  he  has  carefully  watched  and 
marked  particular  insects,  and  has  had  their  nests  under  observation  for  long  ptriotls 
— one  of  his  ants'  nests  having  been  under  constant  inspection  ever  since  lft.74.  His 
observations  are  made  principally  upon  ants,  because  they  show  more  power  and  flexi- 
bility of  mind ;  and  the  value  of  his  studies  is  that  they  belong  to  the  department  of 
original  research." 

"  We  have  no  hesitation  in  saying  that  the  author  has  presented  us  with  the  most 
valuable  series  of  observations  on  a  special  subject  that  has  ever  been  produced,  charm- 
ingly written,  full  of  logical  deductions,  and,  when  we  consider  his  multitudinous  en- 
gagements, a  remarkable  illustration  of  economy  of  time.  As  a  contribution  to  insect 
psychology,  it  will  be  long  before  this  book  finds  a  paraUel." — London  At/ienceum. 

DISEASES  OF  MEMORY.  An  Essay  in  the  Positive  Psychology. 
By  Th.  Ribot,  author  of  "Heredity,"  etc.  Translated  from  the 
French  by  William  Huntington  Smith.     12mo.     Cloth,  $1.50. 

"  M.  Ribot  reduces  diseases  of  memory  to  law,  and  his  treatise  is  of  extraordinary 
mieve&i.'"— Philadelphia  Press. 

"  Not  merely  to  scientific,  but  to  all  thinking  men,  this  volume  will  prove  intensely 
interesting."— xYew  York  Observer. 

"  M.  Ribot  has  bestowed  the  most  painstaking  attention  upon  his  theme,  and  nu- 
merous examples  of  the  conditions  considered  greatly  increase  the  value  and  interest 
of  the  Moivime:'— Philadelphia  North  American. 

"To  the  general  reader  the  work  is  made  entertaining  by  many  illustrations  con- 
nected with  such  names  as  Linnaeus,  Newton.  Sir  Walter  Scott,  Ilorace  Vernet,  Gus- 
tavo Dore,  and  many  others.''''— Harrisburg  Telegraph. 

"The  whole  subject  is  presented  with  a  Frenchman's  vivacity  of  style." — Provi- 
dence Joiirnal. 

"  It  is  not  too  much  to  say  that  in  no  single  work  have  so  many  curious  cases  been 
brought  together  and  Interpreted  in  a  scientific  manner."— Sos^ow  Evening  Traveller. 

MYTH  AND  SCIENCE.     By  Tito  Vignoli.     12mo.     Cloth,  $1.50. 

"His  book  is  ingenious;  ...  his  theory  of  how  science  gradually  differentiated 
from  and  conquered  myth  is  extremely  well  wrought  out,  and  is  probably  in  essentials 
correct." — Saturday  Review. 

"The  book  is  a  strong  one,  and  far  more  interesting  to  the  general  reader  than  its 
title  would  indicate.  The  learning,  the  acuteness,  the  strong  reasoning  power,  and  the 
scientific  spirit  of  the  author,  command  admiration." — New  York  Christian  Advocate. 

"  An  attempt  made,  with  much  ability  and  no  small  measure  of  success,  to  trace  the 
origin  and  development  of  the  myth.  The  author  has  pursued  his  inquiry  with  much 
patience  and  ingenuity,  and  has  produced  a  very  readable  and  luminous  treatise." — 
Philadelphia  North  American. 

"It  is  a  curious  if  not  startling  contribution  both  to  psychology  and  to  the  early 
history  of  man's  development."— iVez^  York  World. 


New  York:   D.  APPLETON  &  CO.,  1,  3,  &  5  Bond  Street. 


D.  APPLETON  &  CO/S  PUBLICATIONS. 


Professor  JOSEPH   LE  CONTE'S  WORKS. 

SIGHT  s  AN  EXPOSITION  OF  THE  PRINCIPLES  OF  MONOCULAR 
AND  BINOCULAR  VISION.  With  numerous  Illustrations.  12mo. 
Cloth,  $1.50. 

•'It  is  pleasant  to  find  an  American  book  which  can  rank  with  the  very  best 
of  foreign  works  on  this  subject.  Professor  Le  Conte  has  long  been  known  as 
an  original  investigator  in  this  department ;  all  that  he  gives  us  is  treated  with 
a  master-hand."— 7%e  Nation. 

ELEMENTS  OF  GEOLOGY  :  A  TEXT-BOOK  FOR  COLLEGES 
AND  FOR  THE  GENERAL  READER.  By  Joseph  Le  Conte, 
LL.  D.,  Professor  of  Geology  and  Natural  History  in  the  University 
of  California.  With  upward  of  900  Illustrations.  New  and  enlarged 
edition.     8vo.     Cloth,  $4.00. 

A  COMPEND  OF  GEOLOGY  :  APPLETONS'  SCIENCE  TEXT. 
BOOK  SERIES.     12ino.     Cloth,  $1.40. 

RELIGION  AND  SCIENCE  :  A  SERIES  OF  SUNDAY  LECT- 
URES ON  THE  RELATION  OF  NATURAL  AND  REVEALED 
RELIGION,  OR  THE  TRUTHS  REVEALED  IN  NATURE  AND 
SCRIPTURE.     12mo.     Cloth,  $1.50. 

"  Professor  Le  Conte  grapples  with  some  of  the  gravest  questions  which  agitate 
the  thinking  world.  He  treats  of  them  all  with  dignity  and  fairness,  and  in  a 
manner  so  clear,  persuasive,  and  eloquent,  as  to  engage  the  undivided  attention 
of  the  reader.  We  commend  the  book  cordially  to  the  regard  of  all  who  are 
interested  in  whatever  pertains  to  the  discussion  of  these  grave  questions,  and 
especially  to  those  who  desire  to  examine  closely  the  strong  foundations  on 
which  the  Christian  faith  is  reared."— 5ostoft  Journal. 

"This  volume  is  written  with  much  clearness  of  thought  and  unusual  clear- 
ness of  expression.  It  is  partly  a  treatise  on  natural  theology  and  partly  a 
defense  of  the  Bible  against  the  assaults  of  modem  science.  In  the  later  aspect 
the  author's  method  is  an  eminently  wise  one.  He  accepts  vvhatever  science  has 
proved,  and  he  also  accepts  the  divine  origin  of  the  Bible.  Where  the  two  seem 
to  conflict,  he  prefers  to  await  the  reconciliation,  which  is  inevitable  if  both  are 
true,  rather  than  to  waste  time  and  words  in  inventing  ingenious  and  doubtful 
theories  to  force  them  into  seeming  accord.  Both  as  a  theologian  and  a  man  of 
science,  Professor  Le  Conte's  opinions  are  entitled  to  respectful  attention,  and 
there  are  few  who  will  not  recognize  his  book  as  a  thoughtful  and  valuable  con 
tribntion  to  the  best  religious  literature  of  the  day."— iViet/;  York  World. 


New  York:   D.  APPLETON   &   CO.,  1,  3,  &  5  Bond  Street 


I).^AXXOSTHAIfl» 

PUBLISHER  a  IMPORTER 

OF 


